ALBERT

Notes: The principle of the mise-á-la-masse method is to earth one current electrode of a pair in a conducting mineral show (in a borehole, in an outcrop etc.) and measure the resulting distribution of electric potentials. The distribution will, to some extent, reflect the geometry of the ore mass of which the mineral show forms a part.In a mise-á-la-masse survey of a lead-zinc deposit in Central Sweden electric potentials were measured on the surface of the ground as well as in some 25 drillholes, in either case with earthings (successively) in three different parts of the irregular ore deposit. Besides this, measurements were made in drillholes with earthings in two further drillholes.Geologic correlation between the drillholes is difficult in the present case on account of the irregular geometry of the ore deposit. However, the mise-á-la-masse measurements clearly showed the dip and the pitch of the ore body, established connections between the different ore widths encountered in the various holes, and yielded information about the shape of the ore mass.In particular, the survey showed that the ore lenses must be crescent-shaped rather than tabular, and the dip was indicated to be westerly, instead of easterly as originally presumed.Three-dimensional models of equipotential surfaces were constructed from the observed drillhole and surface potentials (using transparent plastic sheets and thin copper wire) and these helped to elucidate the mass geometry further.The surface and underground potential data collected in the present case should be of nterest to geophysicists working on analytic continuation problems.

Notes: The author comments the techniques and methods used in continuous seismic profiling by the Monaco Oceanographic Museum during the last five years.Pinger probe give informations on the Mud layering and thickness. On the shelf or in abyssal plains, boomer and sparker are employed and allow to rise various geological conclusions. South coast of France, continental shelf in the Gulf of Lion, abyssal plain of the Ligurian Sea and Lake of Geneva are the areas concerned to with the results.

Notes: The author proposes the parameter Δ2/ΔT1 for possible application in aeromagnetic surveying making use of already available gradiometer systems equipped with sensors separated vertically.

Notes: Geophysical field equipment has undergone rapid changes in the past decade; from simple AGC amplifiers and galvo cameras to binary gain switching amplifiers and digital recorders, all in an attempt to keep pace with the new geophysical interpretive methods developed, and the growing acceptance of the terminology, methods, and philosophy of communication theory.The additional tools of the digital recorder and digital computer make it possible to utilize these new techniques in geophysical processing. Accomplishing these new techniques demands severe requirements on the digital field recording process in handling the decreasing energy return from the seismometer, and to fully realize the capabilities of digital techniques in reducing data. Simple automatic gain control may be used. However, in the more sophisticated interpretive methods, such as autoregression and deconvolution, it is necessary to reconstruct the actual energy levels in the computer. Recording the control signal used in master AGC or programmed gain control may prove satisfactory; however the accuracy of control versus gain is limited to I% for such analog instrumentation.To utilize the computer to its fullest extent, and to accurately perform these new techniques, requires an accuracy of I% or better. This accuracy is obtainable by using a step gain control where the gain is increased by fixed steps in which each step represents a gain in amplification by a constant factor. The accuracy in this case can be made dependent only on the tolerance of resistors used as attenuators or feedback elements. Preferably the constant factor of gain steps should be a number easily handled by the computer. By using 6 db steps it becomes a simple matter to shift binary numbers, such as multiplying or dividing by 10 in the decimal system.The requirements or parameters for such an amplifier system, and the elements of the amplifier necessary to achieve these requirements are presented.

Notes: Spurious reflections showing a residual move-out are generally present on both corrected seismic cross-sections and common depth point composites.We propose to determine a space-time filter satisfying the following conditions: to attenuate as much as possible reflections presenting a given move-out, to retain intact reflections whose time gradient is zero (or has a predetermined value), to be applicable efficiently even to a small number of traces, not to amplify random noise unduly.After briefly indicating the design principle of these filters, we shall give the results of their application to the theoretical examples, in order to bring out: the influence of sampling interval and filter length (possibility of achieving efficient filtering using an apparatus with a small number of terms), the effect of filtering on dipping reflections (reduction in amplitude and distortion increasing with the time gradient), the range of reflection move-out that can effectively be filtered with the same apparatus, the disturbing influence of random noise.〈section xml:id="abs1-2"〉〈title type="main"〉RESUMEOn constate généralement, tant sur les films sismiques corrigés que sur les résultats de couverture multiple, la présence de réflexions parasites présentant une courbure résiduelle d'indicatrice.Nous nous sommes proposé de déterminer un opérateur de filtrage spatio-temporel satisfaisant aux conditions suivantes: filtrer le plus possible les réflexions présentant une courbure donnée, conserver intégralement les réflexions dont le gradient temps est nul (ou a une valeur déterminée), pourvoir être appliqué efficacement à un petit nombre de traces, ne pas amplifier outre mesure les bruits inorganicés.Après avoir indiqué brièvement le principe du calcul de ces filtres, nous présenterons les résultats de leur application à des exemples théoriques, afin de mettre en évidence:ľ'influence du pas d'échantillonnage et de la longueur du filtre (possibilityé d'obtenir un filtrage efficace avec un opérateur comportant un petit nombre de termes),ľ'effet du filtrage sur les réflexions pentées (réduction d'amplitude et distorsion croissant avec le gradient temps),ľ'ouverture de ľ'éventail des réflexions courbes que ľ'on peut filtrer efficacement avec un même opérateur,ľ'influence perturbatrice de bruits inorganicés.

Notes: Consideration is given to the use of a configuration of four electrodes set in a square array for resistivity measurements.It is found that, by passing current successively between different pairs of electrodes, an apparent resistivity can be determined which is both more sensitive to the position of the array centre and less dependent on orientation than the measures usually obtained with colinear arrays of electrodes. At the same time the observations made enable the degree of the departure of local conditions from conditions of lateral homogeneity to be assessed.Theoretical and practical examples of the use of this electrode system are given and the use of the system both as a tool in mapping and in depth investigations is considered.It is shown that provided electrode spacings are suitably arranged the results of a probe carried out using the square array can be interpreted by conventional methods.The system is shown to have particular advantages in the investigation of lateral resistivity variations and the reduced dependence on orientation makes possible the recasting of interpretation data in an orientationally invariant form with a consequent drastic reduction in the number of type curves required for a particular problem.

Notes: A large self-potential anomaly was outlined in 1963–64 at Tantahuatay near Hualgayoc in the Andes of northern Peru. Peak value recorded was–1842 millivolts–thus making it one of the strongest, or perhaps the strongest, SP anomaly ever measured. A lack of detailed geological data precludes the formulation of an adequate explanation for the Tantahuatay anomaly, but geological and mineralogical similarities with the well-documented Venencocha anomaly near Cerro de Pasco, Peru (Kruger and Lacy, 1949), suggest that the anomaly arises from sulfuric acid associated with the mineral alunite. The anomaly obviously cannot be explained by the half-cell mechanism of Sato and Mooney (1960), who place a limit of 700 millivolts on self-potential anomalies over sulfide bodies. Further study of the Tantahuatay anomaly would be of interest in understanding self-potential mechanisms in general.

Notes: Book review in this articleF. S. Grant and G. F. West, Interpretation Theory in Applied Geophysics, McGraw-Hill Comp., New York, 1965, 583 pp., price $ 17.50.Archaeo-Physica. Technische und naturwissenschaftliche Beiträge zur Feldarchäologie. Mit Beitragen von E. Le Borgne, I. Scollar, J. D. Mudie, J. Görier, H.-J. Appel, G. Strunk-Lichtenberg, Böhlau Verlag, Köln, Graz, 1965, 202 pp., 124 fig.H. Takeuchi, Theory of the Earth's Interior, Blaisdell Publishing Company, Waltham (Mass.), Toronto, London, 1966, 131 pp.G. D. Garland, The Earth's Shape and Gravity, The Commonwealth and International Library, Geophysics Division, Pergamon Press, Oxford, London, Edinburgh, New York, Paris, Frankfurt, 1965, 183 pp., price: 17s 6d.

Notes: The electromagnetic field radiated from a magnetic dipole lying on the ground is considered, in the extremely low frequency range (DC to 20 000 Hertz).Theoretical and experimental data are given on the characteristics of the surface wave (vanishing wave) generated at the air-ground interface, in the case of an homogeneous subsurface.The case of a subsurface with electrical resistivity varying with depth is considered.It is shown how the above-mentioned characteristics may be applied in the quantitative investigation of the electrical resistivity of the subsurface as a function of depth, in a method using the measurements on the ground of all the components of the radiated field: horizontal electrical components, vertical and horizontal magnetic components.

Notes: Book review in this articleHandbuch der Physik/Encyclopedia of Physics, Ed.: S. FlüggeThe Aurora. By S.-I. Akasofu, S. Chapman and A. B. Meinel.Time-Variations of Cosmic Rays. By S. E. Forbush.Magnetic Properties of Rocks and Minerals. By T. Nagata.

Notes: A formula is developed for the vertical magnetic field due to an alternating current passing through a long horizontal cable placed on a two-layer ground. The variations of the phase and amplitude ratio of the vertical field, along profiles perpendicular to the cable line are investigated. Within the limits encountered in practice, it is found that if the upper layer is conductive, as compared to the lower layer, the phase may vary appreciably whereas the amplitude ratio changes as in the case of vacuum.

Notes: Book review in this articleN. A. Ogil'vi, D. I. Fedorovich, Groundwater Seepage Rates. English translation by N. H. Choksy, Consultants Bureau, New York 1966, 33 pp., 12 fig.

Notes: Mapping of fault patterns is an important part of geophysical exploration. A computerized digital template analysis method is described which tests gravity maps for the effects of faults by comparing measured gravity data with calculated master curves. The interpreted gravity data are incorporated in a tectonic map using geological symbols and units, for ready use by the geologists.Tectonics can be investigated by gravity detailing if the smallest undulations on the Bouguer map are taken into consideration. Up to now, residual and derivative gravity maps have explained gravity effects by assuming spherical bodies which are almost unknown in geology. The method discussed here uses tectonic elements, such as fault-blocks and dikes as a basis of interpretation instead of the spherical bodies of the conventional interpretation methods.Gravity data can be easily and relatively cheaply obtained in the early phases of exploration by area wide spot coverage following lines of easy access such as roads, etc. Seismic studies, by contrast, have the disadvantage of being executed along predetermined profile lines. Only after sufficient detailing do seismic profiles permit-if at all -an areal mapping of faults. Thus a tectonic map is obtained only at the end of a geophysical survey instead of being available prior to the planning of costly seismic profiles. The use of gravimetric data and their interpretation by the suggested method provides tectonic detail maps in the early phases of geophysical studies.In addition, this article discusses a general geophysical interpretation method, using the investigation of faults by gravity as an example. Applications of this method for different gravity and magnetics problems as well as for combined interpretations are outlined. Detailed case histories will be published in later articles.

Notes: To be able to make use of all existing probe interpretation techniques, it is desirable that field resistivity observations be conducted in such a way that it is possible to construct an equivalent curve for the surface variation of potential about a point source. Further, the usual parallel layer interpretation will only be justified in as much as the observed potential curve is compatible with such a subsurface geometry. Thus, whilst a potential curve may be constructed from suitable finite potential differences obtained using a Wenner configuration of electrodes, it can be shown, using the tri-potential technique of measurements, that these potential differences may arise partly from lateral resistivity variations.In this paper, a ladder network technique is employed to display these lateral effects and an adjustment method proposed to reduce them. The adjusted potential differences obtained form a consecutive series suitable for summation to give the potential function. These values are subject to further minimum adjustments required for them to comply with slope and curvature conditions for a layered medium. After forming the potential curve by summation, a final numerical smoothing process is carried out. From this smoothed potential curve, corresponding Wenner and Schlumberger curves can readily be derived for interpretation.The method proposed thus attempts to extract from the observed data the maximum part which can be reconciled with a purely depth variation of resistivity. A method is also proposed for compounding the ‘errors of closure’ of the network to provide a Lateral Inhomogeneity Index which gives a measure of the departure of the observed data from the basic interpretation requirements.The method involves no great labour, but can readily be programmed for a computer if desired. Examples are given of the application of the method to field observations. In the interest of objectivity, the final smoothing has been confined to a single stage but in certain very extreme examples a further stage may prove desirable.

Notes: In one geophysical survey over a salt dome in the Gulf of Mexico, data taken from a single magnetic and seismic shipborne traverse demonstrated significantly the importance of magnetic measurements. The reduced magnetic and seismic profiles were integrated with gravity measurements from an earlier survey demonstrating the value of obtaining simultaneous geophysical data. The traverse was approximately 25 miles in length, 135 miles southeast of Galveston, Texas. The observed gradient averaged approximately 2 gammas per 1000 feet and crosses the southwest corner of a large shallow salt dome called the Way Dome. The recorded magnetic profile over the salt dome shows a negative magnetic anomaly extending for approximately 12 miles with a maximum amplitude of approximately 20 gammas. This negatively anomaly is due to the negative susceptibility contrast between the salt and cap rock that truncates the surrounding parent sediments. The shape of the negative anomaly correlates well with the continous seismic record and clearly delineates the topographical and structural features of the salt dome. The recorded analog magnetic profile was replotted, with both the regional gradient and time variations removed, which makes the observed anomaly much sharper than is noticeable on the original recorded strip chart record. A theoretical magnetic anomaly was calculated using a computer program for comparison to the observed anomaly. The results showed good correlation.

Notes: The auto-correlation function of a seismic trace contains information on all the multiple reflection activity present in the trace.The interpretation of this information is facilitated by the arrangement of autocorrelation functions in cross-sectional form, in the manner of a normal record section. This is the concept of the Sectional Auto-Correlogram.Specifically, the Sectional Auto-Correlogram will…Show if the record section does not include significant multiples, thus allowing confident picking of the primary reflections.Show if the record section does include significant multiples, giving their travel times and inclinations (and, under certain circumstances, their reflection coefficients).Indicate by what process the multiples should be treated.Yield an authoritative measure of the success of a multiple-attenuating treatment.Delineate shallow horizons, even those whose primary reflections are too early to be recorded satisfactorily.Give the true travel time of a primary reflector, and the sign of its reflection coefficient.The Sectional Auto-Correlogram allows the study of primary reflectors by consideration of the multiples generated by them, and in this sense may be said to turn multiple reflections to advantage. Thus a primary reflection at a certain time is defined if we find that every reflection on the record is followed by a multiple after this certain time. Alternatively, a primary reflection at a certain time is defined if, after that certain time, we can find a repetition of the entire record.The Sectional Auto-Correlogram also has secondary uses in fault identification, crustal studies and weathering problems.

Notes: The development of optically pumped and monitored “atomic” magnetometers has allowed the application of greater resolution in geomagnetic measurements for exploration purposes. This paper presents a survey of instrumentation in use, the variety of exploration techniques that are being used in practice, and an estimate of their state of development.Alkali metals (rubidium and cesium) and helium have been used as active elements to obtain the magnetic-field dependent Larmor frequency. Each of these instruments is capable of obtaining high resolution data (data with sensitivity numerically smaller than one-tenth gamma). They have been adapted for airborne, land, and marine usage.Such sensitivity has enabled the rapid development of geomagnetic gradiometers, high sensitivity aeromagnetics, diurnally reduced ground surveys, broad-band magneto-telluric surveys, susceptibility measurements, and convenient magnetic search and location techniques. Outlines of each procedure and an example of its application are given.

Notes: Amplitudes of the vertical ground motion are larger in the critical angle region than in the near vertical region, especially amplitudes coming from deeper boundaries or interfaces with small velocity contrast. Four basic boundary models are used to derive specific travel time patterns for first order and higher order interfaces. The transition from reflected waves to diving waves in the supercritical angle region is shown for the different models.Examples from wide angle surveys in Bavaria and in the Buchara region in the USSR have many characteristic similarities. Travel time patterns and asymptotic velocities are almost identical. The most important boundaries of the continental crust - the Mohorovč Ić discontinuity and the top of the crystalline basement - correspond to two boundary models mentioned before. Amplitude and frequency investigations have been used to derive items of the M-discontinuity. It is certainly a gradient zone and seems to have a lenticular structure with material of stepwise different velocities.

Notes: When a small, transparent replica of a seismic section is illuminated by a homogeneous beam of coherent, monochromatic parallel light a diffraction pattern is created that is representation of the double Fourier spectrum of the recorded seismic waves, i.e. their spectrum in terms of frequency, f, and apparent wave number, k.Masking selected parts of this diffraction pattern causes the spectrum to be filtered: the recomposition of the filtered spectrum then provides a filtered section.The ideal seismic section for this purpose would be a continuous variable density section obtained from recording made at every point of the seismic line. The light transmission coefficient (in terms of light amplitude) at each spot of the replica should be linearly related to the instantaneous seismic signal strength at the spot on the seismic section to which it refers.Unfortunately we cannot make recordings at every point of a seismic line and in our practically realisable recordings we have to be content with sampling in the direction of the location coordinate x. This means that with variable density recordings aliasing will be present and evident in the spectrum obtained in the direction of k; furthermore, the aliased spectrum is also multiplied by a sine function of k because the recording obtained at a given station is not presented on the seismic section as a single line along the time axis, but occupies the entire width of the trace.The diffraction patterns created by variable density recordings of dipping sine waves, including clipped recordings, and of the effect of dip filtering in such sections are discussed. The efficiency of dip rejection is shown to decrease with increasing dip.The diffraction pattern of a variable density recording is found to be characterised by a relationship between point pairs in the pattern.No such simple relationship has been found for the diffraction pattern of a variable area section; the spectra of such VAR sections belong to a very special class, because the amplitude transmission coefficient has only two values, viz. 0 and 1.Consequently, selective masking of the diffraction pattern of a VAR section may give rise to a filtered profile that does not look like a VAR section at all.General statements about the diffraction pattern of VAR sections are hard to give, because the transmission coefficient at a given point in the replica is not proportional to the signal level in the seismic section at the relevant point.In the case of VAR presentation of harmonic waves it was found that, as well as the aliasing effect in the k direction, higher harmonics of the frequency are also introduced.Some synthetic examples are given that show dip filtering to be less effective with VAR than with variable density recordings.Some arguments are advanced in favour of the opinion that high-pass filtering of VAR sections will have less success than low-pass filtering. This is demonstrated by two synthetic examples.

Notes: The theory is explained and practical applications are shown for a numerical procedure in seismology. Particularly the problems concerning the generation of waves under the action of external pressures, and their propagation, in non-homogeneous, both elastic and absorbing media, have been carried out. These problems have been assumed mono-dimensional and refer to plane and spherical waves.The procedure is based on the solution, by means of series, of the wave differential equation, non-homogeneous, and with non-constant coefficients. It is a direct numerical method whose advantage is, mainly, the possibility of tackling, without great difficulties, problems regarding non-homogeneous elastic and absorbing media.On the contrary the methods which require the theoretical expression of the solutions by means of formulae, generally, present conceptual and numerical difficulties.As examples of application of this procedure, the following cases have been carried out by means of numerical calculations.a) Propagation of a wave, initially of symmetrical shape, in a viscoelastic medium; from the results it appears that the wave propagates without losing its symmetry, i.e. without sensible dispersion. A theoretical analysis has been carried out to justify this result, showing that the dispersion in viscoelastic media is noticeable only for relatively high frequencies. It seems that the practical absence of dispersion in field experiments do not exclude necessarily the viscoelastic character of absorption.b) Generation of plane waves under the effect of a uniform pressure distributed on the plane surface of a medium. The way the length and the shape of the generated wave depends not only on the type of pressure acting on the surface but also on the near surface impedance variations has been studied.c) Generation of a spherical wave under the action of a pressure in a spherical hole.The examples treated show how the length and shape of the wave depends on the radius of the hole. Particularly the frequencies of the wave spectrum are proportional to this radius, for a given type of pressure acting in the hole.The characteristics of this procedure would also permit the study of media for which the stress-strain relations are not univocal and linear (non linear absorption). This study, interesting for the wave propagation in rocks, is worth while to be carried out in a special paper.

Notes: For the computation of the vertical component Hz of the magnetic field of a horizontal A.C. dipole lying on the earth's surface, a recurrence formula is presented for a horizontally stratified half space, to obtain the (n+ 1)-layer case from the w-layer case.By means of several computed diagrams for the two-layer case, Hz can be determined for different ratios of conductivity of the subsoil and that of the overburden. Thereby the distance from the dipole as well as the layer thickness h are expressed in terms of the wave length A of a plain wave in the overburden. Assuming a sufficiently large conductivity difference, the results show that evidence about the subsurface conditions can be obtained if the distance between the measuring coil and the dipole is of the order of A/3, and if the thickness h of the layer varies within the range A/100 〈 h 〈 A/6.As an example for the 3-layer case, a nonconducting intermediate layer is assumed.

Notes: A nomogram is presented which enables evaluation of the components of magnetic attraction of a homogeneous finite rectangular prism, and of gravitational attraction due to a uniform rectangular lamina.In practice any three-dimensional body could be approximated by a number of right rectangular prisms of varying dimensions governed by the shape of the body. The magnetic attraction of the whole body is then obtained by numerical summation of the effects of the constituent prisms.For evaluating the gravitational effect, the cross-section of the body corresponding to each elevation contour is approximated by a number of rectangular laminae (or by a stepping polygon) the attraction of which can be determined with the aid of the same nomogram. The total gravitational attraction of the body is obtained by a process of graphical integration along the vertical axis.

Notes: In [50] and [51] a theory has been developed relating formation factor, permeability and porosity of porous sedimentary rock by means of statistical parameters of the pore system, and further, tying those statistical parameters to other macroscopically measurable quantities like capillarity, capillary retention, flow dispersion etc. This paper deals with experimental methods and apparatus for checking the theoretically derived relations using columns of packed loose or artificially consolidated sands or other granular matter. Some initial experiments, mainly intended for checking out equipment and methods are reported. The discussion of the results so far shows good agreement with the theory in most cases, except for the irreducible water saturation. However, for a definite statement on the general validity of the theory more data must be accumulated.

Notes: Some of the methods such as regional removal and second derivative calculations which can be used to outline anomalies on potential data maps can be thought of as a filtering operation. The analysis and design of such two-dimensional filters by means of direct and inverse two-dimensional Fourier transforms have been considered.An analysis of several published sets of second derivative coefficient sets indicates that, in general, they are not a good approximation to the theoretical second derivative filter. Alternate methods of designing regional removal and second derivative filters are discussed. The properties of various two-dimensional filters are further illustrated by means of maps obtained from the convolution of several of these filters with a set of observed field data. These maps show the large changes in anomaly shape which can result from the inclusion or rejection of various wavelength components.

Notes: Integration of the continuous seismic reflection profiler with the marine refraction method on engineering surveys offers a solution to hidden layer problems, allowing both layer velocity and thickness to be computed.

Notes: This paper is the follow-up of an earlier paper by the same author on the calculation of standard-graphs for horizontally stratified subsoils. The method which was developed in that earlier paper was destined for handwork; it was laid down in master-tables. The present paper deals with the presentation of similar methods to the computer expert in purely mathematical denotation. Two different denotations are described for the calculation of the image pole strengths involved. The first denotation is an improved version of Watsons formulae; it gives the total strengths. The second denotation preserves the character of successive approximations as described in the previous paper. Both denotations have been worked out until a six layer resistivity profile, but actually there is no limitation to the number of layers. There is no restriction to the resistivities of any layer. The only condition is now that all interface depths must be integers.This paper is followed by a paper on the relevant computer program by Argelo in this same issue

Notes: Book review in this articleJ. Frihagen, Electron Density Profiles in Ionosphere and Exosphere, North-Holland Publishing Company, Amsterdam, 1966, price N. fls. 60,–.J. A. E. Allum, Photogeology and Regional Mapping, Pergamon Press, London, 1966, 107 pages, 16 plates, 23 figures, price 17 s 6 d net.

Notes: The common depth point method of shooting in oil exploration provides a series of seismic traces which yield information about the substrata layers at one location. After normal moveout and static corrections have been applied, the traces are combined by horizontal stacking, or linear multichannel filtering, into a single record in which the primary reflections have been enhanced relative to the multiple reflections and random noise.The criterion used in optimum horizontal stacking is to maximize the signal to noise power ratio, where signal refers to the primary reflection sequence and noise includes the multiple reflections. It is shown when this criterion is equivalent to minimizing the mean square difference between the desired signal (primary reflection sequence) and the weighted horizontally stacked traces.If the seismic traces are combined by multichannel linear filtering, the primary reflection sequence will have undergone some phase and frequency distortion on the resulting record. The signal to noise power ratio then becomes less meaningful a criterion for designing the optimum linear multichannel filter, and the mean square criterion is adopted. In general, however, since more a priori information about the seismic traces is required to design the optimum linear multichannel filter than required for the optimum set of weights of the horizontal stacking process, the former will be an improvement over the latter. It becomes evident that optimum horizontal stacking is a restricted form of linear multichannel filtering.

Notes: Book review in this articleW. L. RUSSELL, Principles of Petroleum Geology, McGraw-Hill Publishing Company

Notes: Formulae of the energy spectrum and autocorrelation function have been derived for magnetic anomalies due to four classes of bodies which can be represented in turn by (a) poles, (b) line of poles, (c) dipoles and (d) line of dipoles. The effects of the depth and dimensions of the magnetized sources on the spectrum and the autocorrelation function have been studied. In the case of the dipole models, the orientation of the polarization vector casts a significant influence on the characteristics of the two functions. In all cases, however, the functions change in size and shape as the inclination and declination of the geomagnetic vector are varied.

Notes: The derivation and application of a new method of geomagnetic deep sounding, that is exploring for underground electrical conductivity anomalies by means of temporal variations of the earth's magnetic field, is presented.The problem is restricted to two dimensions (horizontal and vertical) and for the case of a nearly homogeneous horizontal component of the disturbance vector as compared with the vertical over the area in question.The basis of the method is a relationship between both components of the disturbance vector. The first step is a period analysis of the records and from this the construction of so called “characteristic functions”, one for each station, these functions being determined by the conductivity distribution of the earth's interior. The second step consists of a model interpretation of these functions.The method is applied to simultaneous records from five stations (U. Schmucker, 1959) within the region of the conductivity-anomaly of Northern Germany. A preliminary model of this anomaly is given.

Notes: The screening effect of thin, relatively shallow high-velocity layers often presents considerable problems in seismic exploration. Such layers prevent the greater part of the seismic energy from travelling to greater depths and introduce additional refraction arrivals, confusing the seismogram still further.In order to investigate both the screening and refractive properties of high-velocity layers, scale-model experiments have been made over a wide range of layer-thickness/ wavelength ratios (0.05 〈 d/λ 〈 2) for suitably chosen material contrasts. The results may be summarised as follows.Refraction arrivals from thin layers in the field may be recognised by their relatively rapid amplitude decay. Furthermore, the “echeloning”-effect observed for refraction first arrivals may be due to the presence of a (thin) layered structure. Since the apparent refraction velocity varies with d/λ when d/λ 〈 1, differences between vertical well-log velocities and velocities observed along the surface may be expected, making time/depth conversion using surface velocity data inaccurate.Transmission of elastic energy may be expected, if anywhere, only near the shotpoint, at small geophone offset, and for relatively thin screens (d/λ 〈 0.1). The transmitted signal shape is then independent of the layer thickness. This transmitted energy may be registered either in a reflection set-up with geophones near the shotpoint, or in long-distance refraction work.Three possibilities are offered for overcoming the screening effect of thin high-velocity layers: Use longer-wavelength signalsApply short-spread reflection shootingApply long-distance refraction shootingThe experimental results obtained in scale-model arrangements of such set-ups confirm the potentialities of these methods.

Notes: From travel time observations on a test profile ranging from o to 145 km four main events can be distinguished. They represent reflections and diving waves from various discontinuities within the earth crust. A low-velocity zone of a few kilometres thickness begins at a depth of about 10 km, another one probably at 25 km.For the MohoričIć discontinuity (=MD) a gradient zone with a large velocity gradient instead of a first order interface is postulated in order to explain some irregularities of the travel time curve. Comparisons between the to-time of the MD with the statistical data from Dohr and Liebscher show an excellent correlation.〈section xml:id="abs1-2"〉〈title type="main"〉ZusammenfassungAufgrund von Laufzeitbeobachtungen eines Weitwinkelprofils in der Bayrischen Molasse von o bis 145 km Länge können im wesentlichen vier verschiedene Einsätze unterschieden werden, die sich aus Reflexionen bzw. aus Tauchwellen zusammensetzen. Eine Zone geringerer Geschwindigkeit beginnt bei etwa 10 km Tiefe. eine weitere liegt wahr-scheinlich unterhalb 25 km Tiefe. Von den Unregelmäßigkeiten der Laufzeitkurve der MohorovičIć-Diskontinuität (=MD) wird eine Zone mit einem starken Geschwindigkeits-gradienten anstelle einer “scharfen” Grenzfläche abgeleitet. Vergleiche zwischen der to- Zeit der MD-Reflexionskurve mit den statistischen Untersuchungen von Dohr und Liebscher zeigen eine sehr gute Übereinstimmung.

Notes: This paper gives a report about experiments with the geomagnetic field-balance with ribbon suspension of the FANSELAU-type under extreme climatic conditions. These experiments were carried out by several institutions. The results show that the field balances “H” and “Z” give right records even under extreme conditions.

Notes: The design and construction of hydroelectric works, and more particularly of storage reservoirs and dams, in karst areas pose extremely varied and complex engineering, geological and hydrogeological problems, for the solution of which no widely applied techniques have yet been developed.In addition to conventional geological and hydrogeological methods for the study of karst phenomena, the application of more efficient methods of a primarily geophysical nature is called for. These methods, which provide the best means for solving the complex problems encountered in karst, are steadily gaining acceptance.The Miruše storage reservoir and the Grančarevo dam are the key structures in the Trebišnjica hydroelectric complex and are located in an area of typical Dinaric karst. Many of the engineering, geological and hydrogeological problems connected with their design and construction were solved with the aid of electrical geophysical prospecting methods (especially the resistivity method). The investigations provided data on the depth of karstification (the relief of the base level of karst erosion), the position of intensively karstified and tectonically broken zones, as well as on the general orientation of the process of karstification. All these data were helpful in providing a more accurate insight into the impermeability of the rocks that formed the storage reservoir (in relation to the proposed impounding level); they also enabled the consolidation structures (impervious curtains), aimed at preventing excessive losses due to seepage, to be designed more economically.

Notes: High precision gravity surveys have to be examined at different points of view: the accuracy which one can expect on the final results, regardless to their distribution, the shape and amplitude of the expected anomalies, depending on these factors, which grid of stations is convenient in each particular case.Under certain condition, using an appropriate procedure, involving strict criteria, it is possible to get on the Bouguer map the same accuracy as the reading one.However an accuracy closed to 0,01 mgal does not imply that anomalies as 0,01 or 0,02 mgal deserved attention. Numerous factors limit our appreciation of significant anomalies to 0,05 mgal, may be a little less.When cavites are concerned, it is always necessary to define the extreme dimensions an depth of volumes which may give detectable anomalies.Some example are given illustrating different aspects of this particular type of geophysical prospecting.

Notes: Several papers presented at the last SEG Convention in Houston by Schneider, Backus et al have shown how important and fruitful it was to obtain a continuous knowledge of the velocity functions and they have solved their problem by a Dynamic Correlation Analysis. Our purpose is to introduce here a method based on the best summation of a set of traces instead of the best correlation.Practically, this approach has several advantages:1) Two traces only can be correlated at each step whereas the summation can bear on any number of them;2) Optimizing the summation is actually what we are looking for since, at the long end, the success of the improvement is evaluated from the compositing of several traces either weighted or not.On the other hand, an advantage of correlation is the possibility of adding correlations obtained at several places in a same neighbourhood in order to improve the results. With the summation method this is feasible only when dips are inexistent: we shall see that the difficulty due to the dip effect can be turned around.The basic principle of the method can be summed up as follows: traces relating to a same reflection point are considered; several composites are made, each after applying different move out corrections ranging widely around an estimated adequate velocity function. At each time coordinate, the best adapted velocity function, i.e. the one that yields the best phase relation between reflected events, corresponds to the composite trace the average amplitude of which is the largest.This way, the velocity function corresponding to primary reflections as well as those corresponding to multiple reflections can be established accurately.Some examples are shown.

Notes: The problem of elastic waves–from point sources–in layered media is solved in a general and elementary way. Only the simplest principles of the Theory of Functions are necessary. The solutions can immediately be used for numerical applications.

Notes: The symmetry shown, by the function describing the magnetic anomaly due to a dyke or vertical fault step leads to a method by which an observed profile may be adjusted to conform with that symmetry. By making these adjustments a minimum the ideal dyke or fault profile closest to the observations is constructed. In three of four possible situations this is interpreted by simple geometry.Parallelpiped models may be transformed into two dykes for symmetry analysis. Depth limited models are not so amenable, even in special cases.

Notes: The use of digital recorders and computers in seismic exploration promises major enhancement of the quality of final documents available to interpreters. The ultimate objectives of recording and processing remain what they always have been:1 Record the reflection wavelet as a function of time; this requirement has been met with satisfactory accuracy for a number of years.2. Record the reflection wavelets with sufficient fidelity to permit the interpreter to recognize them.Various factors affect our ability to achieve this second objective. Certain recording errors are associated with digital recording systems. However, an understanding of the sources of error will enable the operator to use his system properly and to estimate the noise level or inaccuracy of field recordings. Field operations do not require rigorous error analysis; in most cases a satisfactory approximation can be obtained from simple calculations.Three types of “noise”–seismic, instrument and power line–introduce errors. Factors which contribute to over-al recording system error include specifically input noise, power supply ripple, crosstalk, A-D conversion error, quantizing noise, aliasing, distortion. Examination of each component of a recording system, permits the determination of its ultimate effect on the over-all noise level–or error level–of the entire system.Many of the error sources produce statistically independent noise which is not correlative. Where this is true, error voltages from various sources may be combined by taking the square root of the sum of the mean square noise voltages, giving a result slightly greater than the largest single voltage if one source is much greater than any other source. This simplification can be used to estimate over-all system noise levels. Distortion and crosstalk depend on signal amplitude and should be added algebraically in each category. Each final sum should be used as a statistically independent noise source with respect to other system noise sources.Using the foregoing examples and simplified system for estimating over-all system noise, and assuming that much of the distortion (which limits signal/instrument noise ratio to 54 db) can be removed by filtering, we determine that the combined effect of all sources of error is to reduce the system S/N ratio to approximately 74 db.With proper care digital field recording systems can produce very good field records, and exotic computer processes can enhance signal and reduce various forms of noise. However, one always must recall that the level of confidence which one can place in an interpretation of seismic data must be dependent on a knowledge of the accuracy of the basic data.

Notes: The Terrapak is a new seismic energy source of the surface energy source type. Essentially, the Terrapak consists of a compressed air piston which transmits a shock to the ground by means of a striker plate attached to the piston rod. The Terrapak is truck-mounted together with its ancillary equipment. Shocks can be generated at 8 second intervals, and although the weight of the striker is relatively low (approximately 1400 Ibs) the impact velocity exceeds 66 ft/sec. The energy available is about 85,000 ft. lb., which is equivalent to that produced by conventional weight-dropping methods. The power spectrum of the seismic wave produced by the Terrapak is spread out towards the higher frequencies because its impact velocity is greater than that of a dropping weight.There is a noticeable difference between noise records made with the Terrapak and noise records made with a conventional weight-dropping technique. The same noise frequencies are found in both cases, but low frequency noise is stronger with weight dropping than with the Terrapak, whereas the intermediate frequency reflections obtained using the Terrapak are more suitable for correlation.The expansion of the compressed air generates a sound wave, the effects of which must be eliminated by the use of multiple geophone arrays. A spectrum analysis of the records has confirmed that the waves produced by the Terrapak are rich in intermediate frequency components. This facilitates the picking of reflections in normal areas where the apparent frequency of the reflections is about 30 to 35 c/s.

Notes: This paper includes publication of two algorithms, to be processed on a digital computer. The algorithms are based upon the two mathematical denotations, presented by Dr. J. C. van Dam in this same issue. The computer programs are written in Algol, in the form of procedures (i.e. subroutines to be activated from a surrounding Algol program).Each of the two procedures is preceded by a numerical analysis. Some remarks are made about the reliability of each of the two procedures, the production and the computing time required.

Notes: The auto-correlation function of a seismic trace contains information on all the multiple reflection activity present in the trace.The interpretation of this information is facilitated by the arrangement of autocorrelation functions in cross-sectional form, in the manner of a normal record section. This is the concept of the Sectional Auto-Correlogram.Specifically, the Sectional Auto-Correlogram will.Show if the record section does not include significant multiples, thus allowing confident picking of the primary reflections.Show if the record section does include significant multiples, giving their travel times and inclinations (and, under certain circumstances, their reflection coefficients).Indicate by what process the multiples should be treated.Yield an authoritative measure of the success of a multiple-attenuating treatment.Delineate shallow horizons, even those whose primary reflections are too early to be recorded satisfactorily.Give the true travel time of a primary reflector, and the sign of its reflection coefficient.The Sectional Auto-Correlogram allows the study of primary reflectors by consideration of the multiples generated by them, and in this sense may be said to turn multiple reflections to advantage. Thus a primary reflection at a certain time is defined if we find that every reflection on the record is followed by a multiple after this certain time. Alternatively, a primary reflection at a certain time is defined if, after that certain time, we can find a repetition of the entire record.The Sectional Auto-Correlogram also has secondary uses in fault identification, crustal studies and weathering problems.

Notes: The development of optically pumped and monitored “atomic” magnetometers has allowed the application of greater resolution in geomagnetic measurements for exploration purposes. This paper presents a survey of instrumentation in use, the variety of exploration techniques that are being used in practice, and an estimate of their state of development.Alkali metals (rubidium and cesium) and helium have been used as active elements to obtain the magnetic-field dependent Larmor frequency. Each of these instruments is capable of obtaining high resolution data (data with sensitivity numerically smaller than one-tenth gamma). They have been adapted for airborne, land, and marine usage.Such sensitivity has enabled the rapid development of geomagnetic gradiometers, high sensitivity aeromagnetics, diurnally reduced ground surveys, broad-band magneto-telluric surveys, susceptibility measurements, and convenient magnetic search and location techniques. Outlines of each procedure and an example of its application are given.〈section xml:id="abs1-2"〉〈title type="main"〉ResumeEn détection des richesses du sol, “les magnétomètres atomiques” qui fonctionnent selon le principe ?un pompage optique ont permis ?obtenir des mesures plus sensibles. Sont décrits les appareillages actuellement utilisés, les méthodes de mesure différentes, ainsi que la situation technique récente.La génération de la fréquence Larmor qui dépend du champ magnétique s'obtient par les métaux alcalins (le rubidium, le césium) et par ľhélium. Chacun des instruments utilisés fournit des résultats de résolution fine, inférieure au dixième du gamma. Des équipements furent réalisés pour ľutilisation aéroportée, sur navire, ainsi que sur terre.De telles sensibilités élevées ont été rendues possibles grâce aux nouveaux gradio-mètres, aux aéro-magnétomètres extra-sensibles, aux mesures des profils terrestres avec correction diurne, aux investigations magnéto-telluriques large bande, aux mesures de susceptibilityé et aux méthodes pratiques de recherche magnétique.Le sommaire explique les principes à la base et les applications de tous ces proédés.

Notes: Downward continuation of the field in the neighborhood of a singularity of a magnetic anomaly is used to render the anomaly more two-dimensional, to make the bottom of the causal body more remote, and to obtain an auxiliary function, φ (O, z), by means of which the anomaly may be interpreted in terms of an equivalent vertical contact or step model. The concept of “apparent depth” is introduced and used in studying depth extent and susceptibility. The methods are illustrated with theoretical and practical examples.

Notes: Refraction along thin high velocity layers and along basement is investigated in two cases.a) high velocity layer just on the basement.b) high velocity layer higher above.Period and attenuation of refracted waves are given as a function of the layer thickness H. Refracted arrivals along thin high velocity layers are visible at significant distances if the layer thickness is not smaller than A/6, where A is the longitudinal wavelength in high velocity medium. the pseudoperiod is proportional to the layer thickness H. The attenuation at large distance follows an x−n e−k1x law, where n is close to I and R1 is inversely proportional to H.Refracted arrivals along the basement are observable even in the case of thin high velocity layers situated in the overburden; their intensity is smaller and their pseudoperiod larger than when no layer exists in the overburden. The intensity of the basement arrival decreases and the pseudoperiod increases with increasing laer thickness.The pseudoperiod and the attenuation of refracted arrival along high velocity layers and along the basement are also highly dependent on acoustic contrasts.Both arrivals from a high velocity layer and from the basement can be recorded simultaneously, provided the frequency spectrum of the seismic cbain is sufficiently broad. IN all cases layer arrivals show a character very different from basement arrivals.〈section xml:id="abs1-2"〉〈title type="main"〉RESUMELa refraction le long des bancs minces rapides et du socle moins rapide sous-jacent, est etudiee sur modeles dans deux cas:a) banc rapide reposant directement sur le socle;b) banc rapide situe plus haut dans le recouvrement.La period et l'attenuation des ondes rerractees sont donnees en fonction den l'epaisseur H du banc rapide. Les arrivees refractees le long des bancs rapides ne sont pas visibles sur une distance importante si l'espaisseur de ces bancs est inferieure a A/6 A designant la longueur d'onde longitudinale dans le milieu rapide. La pseudoperiode est proportionnelle a l'epaisseur H du banc. L'attenuation a grande distance suit une loi eb x−n e−k1x avec n voisin de l et k1 inversement proportionnel a H.Les arrivees refractees le long du socle sont observables en presence de bancs minces rapides dans le recouvrement, mais avec des internsites plus faibles que dans le cas d'unrecouvrement homogene. La pseudoperiode des impulsions refractees du socle augmente avec l'epaisseur H du banc rapide. L'attenuation en fonction de la distance est superieure a l'attenuation observee pour un recouvrement homogene, et elle croit avec H.La pseudo-periode et l'attenuation des arrivees refractees le long des bancs rapides et des marqueurs sous-jacents sont largement fonction des impedances acoustiques des milieux en presence.Les arrivees d'un banc mince rapide et socle peuvent etre observees simultanement a condition que la chaine d'enregistrement ait un spectre en frequence suffisamment large. On constate dans tous les cas que le caractere des arrivees des bancs est tres different du caractere des arrivees du socle.

Notes: The term “structure”, as used here, includes synclinal and anticlinal folds and folding in general, faults, cross fractures and various conditions associated with intrusions. Structure, both regional and local, has a very important role in emplacement of mineralization. Under certain circumstances which occur fairly commonly, structural conditions are reflected significantly in the trends and intensities apparent on aeromagnetic maps. A number of documented illustrations based on Canadian Shield conditions are discussed. Illustrations are drawn from areas of known geology and from proven mining camps, as well as from loci of recent discoveries. Canadian examples are chosen because of existence and availability of extensive aeromagnetic cover, although it is logical to extend the argument to other shields and indeed to regions of other geological, but similar magnetic character.The importance of aeromagnetics in structural approach to exploration and the correctness of such approach seem to be fully substantiated by results discussed.

Notes: The paper describes a transistorised, portable proton precession magnetometer constructed for surface geophysical prospecting. Constructional and circuit details are furnished. The readout of the instrument is digital. The accuracy of measurement is ± 1 part in 20,000. The maximum gradient of the total field under which a satisfactory measurement can be made is about 1 gamma/cm. The sensing head uses a single coil system with distilled water as the proton sample.

Notes: Book review in this articleJ. L. Worzel, Pendulum Gravity Measurements at Sea, John Wiley & Sons, London and New York, 1965, Price 210 sh.D. S. Parasnis, Mining Geophysics, Elsevier Publishing Company, Amsterdam-London-New York, 1966, XVI + 356 pages, 11 tables, 128 illustr., Price N. fls. 50,–.K. Ya. Kondrat'yev, Radiative Heat Exchange in the Atmosphere, Leningrad, English edition, Pergamon Press.

Notes: A brief review of the existing methods of gravity reduction is given and a new method suitable for use on high speed digital computers is described. The method is based on the formula for the gravitational attraction of a frustum of a cone. The topographic contours are represented by polygons and the x and y coordinates of corners of the polygons constitute the input to the computer. The vertical component of the gravitational attraction is calculated by evaluating the cone formula for a number of vertical sections of the topography. Each vertical section is simplified by adopting a procedure of grouping and averaging for the distant points of the section. The effect of the earth's sphericity is taken into account by lowering the distant points of the sections by amounts determined by the curvature. The computations include the area close to the point at which the attraction is required and may be limited to an area defined by a circle centered at this point. The method is therefore compatible with the conventional zone chart methods.As an illustration of the method the gravitational attraction of Caryn Seamount in the Atlantic Ocean is computed. The total Bouguer correction and the Terrain correction are also computed for an area in northwestern South America and comparisons are made with hand computations by a zone chart method. As an example, for work at sea, the Bouguer corrections for an area near the Island of Mauritius in the Indian Ocean are computed and the effects of sphericity and three-dimensionality are calculated.The gravitational attraction of two-dimensional bodies can be computed in a very similar manner. The attraction of the Puerto Rico Trench model is computed and the results are compared with other methods. The effects of sphericity and assumptions involved in extending the models to infinity are discussed.

Notes: A description of planning, organisation and field procedure of a test profile of 150 km length is given. This profile was laid out as an experiment for a detailed investigation of the velocity–depth–structure of the earth's crust in a selected area. The line was to be shot as a wide angle profile with a common reflection point.

Notes: The region of Graus (Central Spanish Pyrenees) has been surveyed by the conventional seismic reflection method in the years 1963–64.This region is strongly accidented and there are only a few roads of access. Thus a good grid of seismic lines could not be realised. Therefore a seismic survey with completely portable equipment was tried out. For that reason drilling was abandoned.The results seem to show that the method of the air-shots is completely comparable with that of buried shots.

Notes: An ill-defined seismic marker has been identified as the top of the sandstone lower Trias in the “Landes”– small area within the whole Aquitaine region for which the S. N. Repal obtained prospecting licences. Before any drilling was made, this marker was thought to belong to the early saliferous triassic series.The quantitative use of the residual gravity anomaly has made the seismic reflection interpretation easier. This interpretation was found to give excellent results along the coastline where all postulated hypothesis proved true in the bore holes of Contis and St Girons.As a first approximation, it appears that the substratum of the saliferous bed in sub-horizontal and has a fairly steady gravity. The Jurassic and the Cretaceous, both limestones, are prevailing (0,15) in comparison with the argillaceous-saliferous Trias and the early Tertiary which was revealed to us with accuracy through seismic surveys. The use of an approximative linear equation where the gravimetric residue is expressed as a function of the limestone thickness allows a better seismic interpretation.This makes possible a more reliable approach of the structural study of post-triassic deposits. The same holds good for the sandstone substratum which shows on an isochronous map strains due to thickness and velocity changes in the overburden. These facts help us to get a better insight into the origin and formation of salt accumulations in this particular area.

Notes: Book review in this articleBarsukov, Blinova, Vibornyky, Gulin, Pakhnov, Larionov and Kholin, Radioactive Investigations of Oil and Gas Wells, English Translation by Muhlhaus, Pergamon Press, 1965, 300 pp., 140 fig.Stuart R. Kaplan (editor), A Guide to Information Sources in Mining, Minerals and Geosciences, Vol. 2, Interscience Publishers, Division of John Wiley & Sons, New York, London, Sydney, 1965, price 95 s.F. J. Pettijohn and P. E. Potter, Atlas and Glossary of Primary Sedimentary Structures, in English, Spanish, French, German, Springer-Verlag, Berlin, Göttingen, Heidelberg, New York, 1964, 117 plates, XVI, 370 pp., cloth DM 59,–.J. Coulomb and G. Jobert, The Physical Constitution of the Earth, translated by A. E. M. Nairn, Publishers Oliver & Boyd, Edinburgh and London, price: 50 s.G. A. Gamburzew, Grundlagen seismischer Erkundung, German Edition, Leipzig, 1964, pp. 430, 271 fig., price MDN 51,–.

Notes: The theory of statistical communication provides an invaluable framework within which it is possible to formulate design criteria and actually obtain solutions for digital filters. These are then applicable in a wide range of geophysical problems. The basic model for the filtering process considered here consists of an input signal, a desired output signal, and an actual output signal. If one minimizes the energy or power existing in the difference between desired and actual filter outputs, it becomes possible to solve for the so-called optimum, or least squares filter, commonly known as the “Wiener” filter. In this paper we derive from basic principles the theory leading to such filters. The analysis is carried out in the time domain in discrete form. We propose a model of a seismic trace in terms of a statistical communication system. This model trace is the sum of a signal time series plus a noise time series. If we assume that estimates of the signal shape and of the noise autocorrelation are available, we may calculate Wiener filters which will attenuate the noise and sharpen the signal. The net result of these operations can then in general be expected to increase seismic resolution. We show a few numerical examples to illustrate the model's applicability to situations one might find in practice.

Notes: In order to adequately understand the complicated, anelastic processes governing wave propagation in soils or highly weathered rock it seems desirable first to have available a convenient laboratory material for such propagation studies the frequency dependent rheological parameters of which are known beforehand. A property measurement program has been conducted to determine the complex Young's modulus and the complex shear modulus of a commercially available viscoelastic material over a broad spectral region.

Notes: In the year 1958 the Service for Water Management of the „Rijkswaterstaat” started its program of geo-electrical resistivity prospecting in the western part of the Netherlands. The aim of this program was to obtain data on the salinity distribution of the ground water.The ground water regime in this part of the Netherlands is most intricate. This is due to the geological and geo-hydrological conditions and to the low elevation of the land. Many reclaimed areas are up to several metres below mean sea level.The resistivity data obtained are closely related to the salinity of the ground water. On the basis of bore hole data it was even possible to arrive at calibration curves for the salinity of the ground water in sand deposits. Under special conditions it was also possible to draw conclusions with respect to the presence of less permeable formations as e.g. clay layers.Some remarks are given on the practical performance and the interpretation of the measurements.A review is given of the work done until now. Some results are shown by means of maps of the salinity distribution of the ground water in the western and northern parts of the Netherlands.Two examples are described of the use of the data obtained during the survey in the province of Zuid-Holland.Another two examples are presented of detailed investigations for special purposes in relatively small areas.

Notes: In mountainous areas it is an inadequate procedure to reduce gravity observations by merely subtracting the effect of an infinite flat slab of material between the station and sea-level, and adding a terrain correction. A programme is described which directly computes the effect of masses above sea-level, and mass-deficiencies below it; as well as the effect of compensating masses under the Pratt and Airy isostatic systems. As an example, the method has been applied to a regional gravity survey of Papua and New Guinea where it is seen to remove the usually high correlation of the Bouguer anomaly with local topography.

Notes: The common depth point method of shooting in oil exploration provides a series of seismic traces which yield information about the substrata layers at one location. After normal moveout and static corrections have been applied, the traces are combined by horizontal stacking, or linear multichannel filtering, into a single record in which the primary reflections have been enhanced relative to the multiple reflections and random noise.The criterion used in optimum horizontal stacking is to maximize the signal to noise power ratio, where signal refers to the primary reflection sequence and noise includes the multiple reflections. It is shown when this criterion is equivalent to minimizing the mean square difference between the desired signal (primary reflection sequence) and the weighted horizontally stacked traces.If the seismic traces are combined by multichannel linear filtering, the primary reflection sequence will have undergone some phase and frequency distortion on the resulting record. The signal to noise power ratio then becomes less meaningful a criterion for designing the optimum linear multichannel filter, and the mean square criterion is adopted. In general, however, since more a priori information about the seismic traces is required to design the optimum linear multichannel filter than required for the optimum set of weights of the horizontal stacking process, the former will be an improvement over the latter. It becomes evident that optimum horizontal stacking is a restricted form of linear multichannel filtering.

Notes: Downward continuation of the field in the neighborhood of a singularity of a magnetic anomaly is used to render the anomaly more two-dimensional, to make the bottom of the causal body more remote, and to obtain an auxiliary function, φ (O.z), by means of which the anomaly may be interpreted in terms of an equivalent vertical contact or step model. The concept of “apparent depth” is introduced and used in studying depth extent and susceptibility. The methods are illustrated with theoretical and practical examples.

Notes: Refraction along thin high velocity layers and along basement is investigated in two cases.a) high velocity layer just on the basement.b) high velocity layer higher above.Period and attenuation of refracted waves are givers as a function of the layer thickness H. Refracted arrivals along thin high velocity layers are visible at significant distances if the layer thickness is not smaller than A/6, where A is the longitudinal wavelength in high velocity medium. The pseudoperiod is proportional to the layer thickness H. The attenuation at large distance follows an x-ne-k1x law, where n is close to I and k1 is inversely proportional to H.Refracted arrivals along the basement are observable even in the case of thin high velocity layers situated in the overburden; their intensity is smaller and their pseudo-period larger than when no layer exists in the overburden. The intensity of the basement arrival decreases and the pseudoperiod increases with increasing layer thickness.The pseudoperiod and the attenuation of refracted arrivals along high velocity layers and along the basement are also highly dependent on acoustic contrasts.Both arrivals from a high velocity layer and from the basement can be recorded simultaneously, provided the frequency spectrum of the seismic chain is sufficiently broad. In all cases layer arrivals show a character very different from basement arrivals.

Notes: This report gives a description of Fortran II programs for filtering and spectral analysis. All programs are tested.

Notes: In the inductive method of prospecting, information on conductivity and size of conducting ore-bodies located in non-conducting host rocks, can be conveniently obtained by studying amplitude-frequency relation or amplitude-phase relation of their response with the help of suitable Master-curves. Experiments carried out in the laboratory on the scale-model method show these Master-curves to be different depending on the type of primary excitation and the shape of conductor. Cases of sphere, plate and disc in uniform field, field of line source and dipole field have been studied with an Amplitude-Phase Meter specially constructed in the laboratory for this purpose.

Notes: The occurrence of shingling in. long range refraction records often makes the task of the seismic interpreter heavier, especially when several refractors are encountered and the velocity contrasts are small.The explanation of the phenomenon given by the existing literature is examined and the theoretical results are compared with the observed data on field records.In field seismograms shingling must be separated from the effect of geological structures or lateral discontinuities.If an appropriate analysis of shingling is possible, this phenomenon can be related to the type of refracting layer, being a useful tool to a qualitative approach.On the other hand the implications of shingling are examined on the side of the geometrical interpretation

Notes: The knowledge of hydraulic and electric properties of porous media and the relations between them is essential for the quantitative evaluation of electric well logs and the solution of other reservoir engineering problems. The state of the art in this field is not yet satisfying. Theories still show considerable discrepancies with practice due to oversimplified model approaches. Empirical relations are either too coarse, not fully determined, or valid under specific geological and geographical conditions only. This article deals with the development of a general theory of the electric and hydraulic resistance behavior of porous media on the basis of a very general statistical network model. A general solution of the relations between formation factor, permeability, and porosity is presented by means of a rigorous mathematical treatment of two limiting cases of such a network. The solution shows that the product of the formation factor and the permeability can be expressed in the expectation values and the variation coefficients of pore channel cross section and shape factor and by a network factor, that depends on the mesh texture of the network. This network factor is in the range zero to one. It is further shown that the path length increase enters both the electric and the hydraulic tortuosity by its square.

Notes: A simple method of magnetotelluric interpretation is derived using the property that the earth currents flow in horizontal sheets. It is shown that when the depth is taken as two-thirds of the Cagniard's depth of penetration (Cagniard, 1953), the mean resistivity-over the depth is the same as the apparent resistivity of the medium. From a mean resistivity versus depth of penetration plot, resistivity can be easily computed at all depths of the sounding.This method gives satisfactory results in a short time and makes it possible to interpret the soundings over media of several layers. However, the results are inaccurate near maximum and minimum points of the plot as well as in the zone of thin layers.

Notes: The authors propose a method of determining the sedimentary composition of the sea-bottom by studying the variation of the frequency contents of the consecutive multiple reflections between bottom and surface of the sea.

Notes: In a previous paper by the present author a method was developed for direct interpretation of resistivity observations made with a Schlumberger electrode configuration. This method consisted of two steps. The first of these was to derive the kernel function in the integral expression for the apparent resistivity from the observed data; the second step was to derive the resistivity stratification from this kernel function.The first of these two steps depends on the electrode configuration that has been used. In the present paper the above mentioned method is modified so as to make it apply to a Wenner electrode configuration. The procedure is indicated by which the method may be adapted to any other electrode configuration in which the distances between the electrodes are finite.The second step in the interpretation, i.e. the derivation of the resistivity stratification from the kernel function, is independent of the electrode configuration used, and therefore needs no further discussion in the present context.

Notes: Judges rated the intensity of NaCl solutions and orange drinks of varying sweetness using category scales and line scales. They performed under four response conditions that varied in reliance on memory: (1) verbal response (2) written response with no retasting and the response sheet removed (3) written response with a single response sheet which allowed past scores to be reviewed and amended but with no retasting (4) the same as ‘3’ but with retasting. Discrimination errors decreased from conditions ‘1’ through ‘4’ indicating how allowing judges to ‘refresh the memory’ improved discrimination. The cognitive processes involved in rating and consequences for scaling protocols and the experimental design for descriptive analysis are discussed in the light of these findings.

Notes: The effects of sweetener type, sweetener concentration, and fruit flavor on the sensory attributes of soy fortified yogurt were determined. Soy fortified dairy yogurts were made by the addition of soy protein concentrate (0, 2.5, 5%) to standard yogurt mixes prior to fermentation. Sweetener type (sucrose, fructose, sucrose/fructose) and sweetener concentration (6, 8, 10%) were incorporated into yogurts in a split plot experiment with soy concentration as a subplot factor. Flavor effects (plain, lemon, strawberry) were studied in a 3 × 3 factorial experiment (soy concentration × flavor). A trained descriptive panel (n=13) evaluated yogurts for seven flavor and aroma terms. Sweetener type had no effect on sensory properties with the exception of perceived sweetness. Soy flavors and astringency decreased with increasing sweetener concentration. Fruit flavors decreased soy aromas, soy flavors, and astringency in yogurts containing soy protein. These results indicate that sweetener concentration and fruit flavors play a crucial role in formulating yogurts fortified with soy protein.

Notes: A two-part study determined the effectiveness of gum-based rinses with or without oil for alleviating residuals of a bitter (0.8 g/L caffeine solution) and an astringent (1g/L alum solution) stimuli in serial responses using a sip and spit method. In Experiment 1, rinsing with deionized water was compared to rinsing with 0.3% xanthan gum in water alone or with 5% corn oil and 0.55% carboxymethyl cellulose (CMC) in water alone or with 5% or 10% corn oil. The 0.3% xanthan gum and 5% corn oil mixture resulted in the highest stimulus intensity difference before and after rinsing, whereas 0.55% CMC had a value of nearly zero for residual effect. Results of a two-alternative forced choice test used in Experiment 2 indicated that both were equally effective for reducing bitterness residuals, but 0.55% CMC solution resulted in the lowest (p=0.007) residual effect for astringency. Therefore, the 0.55% CMC rinse was considered an effective interstimulus rinse to use for assessing both bitterness and astringency in model solutions.

Notes: For discrimination tests not requiring the nature of the difference to be specified in the instructions, such as the triangle, duo-trio and same-different protocols, it is usually assumed that the decision rule used by the subject in order to generate an answer involves the comparison of the relative sensory distances between the samples. However, there is evidence that an alternative cognitive strategy, the β-strategy, involving the absolute categorization of the sensations could be used by the subject when performing these protocols. This paper introduces the characteristics of this alternative strategy by discussing its statistical power (higher than the traditional strategies) and by describing means of investigating which strategy is used by the subject during an experiment as well as illustrating the experimental conditions that might facilitate the use of this particular decision rule.

Notes: The perception of astringency and basic taste in mixtures and their interaction effects were investigated by two procedures. In Experiment 1, focused and nonfocused testing procedures were compared using mixtures of low and high concentrations of alum and basic taste solutions. Both procedures yielded taste and astringency intensities that were modality-dependent. Nonfocused testing was used in Experiment 2 to investigate the interactions of astringent phenolic (tannic acid) and nonphenolic (alum) compounds with each basic taste. Sweetness of sucrose increased with increased concentration with or without alum or tannin present. Changes in salty, bitter, and sour taste intensities were modality-dependent. Astringency either remained unchanged or decreased with the addition of sucrose, sodium chloride, citric acid, or caffeine depending upon the taste concentration. Bitterness of tannin and alum at high concentrations was suppressed by the addition of sucrose, sodium chloride, or citric acid; sourness also decreased in the presence of sucrose or sodium chloride as well as a high level of caffeine.

Notes: Principal component similarity (PCS) analysis was used to evaluate judge performance from a wine competition. Data were analyzed for five international judges and seven wine makers, for 42 white, 30 red and 25 specialty wines, using a 20-point quality scoring system. Principal similarity plots were used to group judges according to judging 'style’ and to identify outliers, for each wine category. Judge groupings were consistent when three different references were used; however, the most interpretable PCS plot was obtained when the overall mean-judge-score was used as the reference. Results from PCS were compared to principal component analysis (PCA). PCS analysis allowed the information from all significant principal components to be graphically represented in two dimensions and was more successful in classifying judges than plots based on the first three principal components. The technique of PCS is an important complement to existing methodologies, and can provide wine competition coordinators with an objective technique for judge evaluation and selection.

Notes: Exact tables calculated directly from the probability function of a beta-binomial distribution are provided for replicated difference and preference tests. The tables can be used for small experiments when the numbers of replications and trials are not more than five.

Notes: Dependence among responses in using the A-Not A or “ Yes-No” task are accounted for in new hypothesis testing models. The new models involve adjustments to Pearson's and McNemar's chi-square statistics and to the variance of d', a measure of signal detectability or sensitivity.

Notes: Anecdotal evidence suggests that astronauts’ perceptions of foods in space flight may differ from their perceptions of the same foods on Earth. Fluid shifts toward the head experienced in space may alter the astronauts’ sensitivity to odors and tastes, producing altered perceptions. Our objective was to determine whether head-down bed rest, which produces similar fluid shifts, would produce changes in sensitivity to taste, odor or trigeminal sensations. Six subjects were tested three times prior to bed rest, three times during bed rest and two times after bed rest to determine their threshold sensitivity to the odors isoamylbutyrate and menthone, the tastants sucrose, sodium chloride, citric acid, quinine and monosodium glutamate, and to capsaicin. Thresholds were measured using a modified staircase procedure. Self-reported congestion was also recorded at each test time. Thresholds for monosodium glutamate where slightly higher during bed rest. None of the other thresholds were altered by bed rest.

Notes: The effect of liking, brand and price label on purchase intention were studied on crisp snacks in branded, supermarket own label and economy form. Unlabeled assessment segregated the products into differing levels of liking which did not correspond to marketed price and brand location. Level of liking dominated purchase intention under partial label (price or brand alone) and full label (price with brand) conditions. Relative and derived purchase intention measures gave clearer label effects with significance for brand and price. Consumers who professed higher price awareness were more influenced by price, but those professing brand as a main purchase intention reason gave more weight to liking. Results from analysis of purchase intention and degree of liking measures according to private body conscious level were inconclusive.

Notes: Forty pure chemical compounds representing a wide range of odors, were evaluated by a panel of 240 consumers. These compounds were matched with a list of 40 common descriptors. The results were analyzed by Correspondence Analysis and Hierarchical Clustering. This original approach enhanced the study by providing a layman's point of view and thereby shedding light on the theories of olfactory perception. The level of odor confusion by consumers was also studied. Consumers pointed out three principal odorant directions which we called “ citrus”, “ sweet” and “ heavy” . Aniseed and garlic odors were the most isolated notes. The association among compounds or odors was explained by semantic processes and by the odorant products consumers used which make up their odorant domain.

Notes: This paper presents a set of analyses on sensory directional attributes used to rate experimentally designed pizza products. Consumers may or may not know the ‘optimal’ sensory level of attributes for pizza, so that the usefulness of the sensory directional varies by attribute. Furthermore, the sensory magnitude of each sensory directional attribute varies, as shown by the slope (B) relating the two attributes (Sensory Magnitude = A + B (Directional Rating)). The study incorporated sensory directionals into evaluation of products varied according to an experimental design. The optimal product emerging from the design does not necessarily exhibit a sensory directional profile where all attributes are ‘on target’, nor does a product whose sensory attributes are all on ‘target’ exhibit the highest level of liking.

Notes: Cluster analysis, consonance analysis, principal component analysis (PCA) and the GRAPES program (Schlich 1994) were compared for the evaluation of panel performance. Ten judges evaluated 25 Merlot wines for 24 color, aroma and flavor attributes. Cluster analysis grouped similar judges. PCA identified judges according to their attribute use. Consonance analysis determined a numerical index for attribute agreement and the GRAPES program compared judges in their use of the scale, reliability, discrimination and disagreement. Three of the four techniques provided a graphical representation of similarities and differences between judges. Methodologies were best used in conjunction with one another. Ultimately the application of these tools will serve to improve the quality of sensory evaluations.

Notes: This study examines the effect of beer assessment training on verbal and nonverbal performance. Two groups of subjects are asked to sort, match, and describe a set of 12 beers (6 supplemented and 6 commercial beers). Subjects from the first group are enrolled in a beer-training program. Subjects in the second group are untrained beer consumers. Results show that although both groups perform the matching task equally well, trained subjects performed better on supplemented beers and untrained subjects on commercial beers. Examination of the generated vocabulary shows that 44% of the terms are common to trained and untrained subjects. However, an analysis of the terms’ efficiency shows that whereas for trained subjects, precise terms are more efficient than intensity or hedonic terms; the opposite is observed for untrained subjects. This suggests that it is not the term itself that is important but the common reference associated to it.

Notes: Quantifying flavor in fruit concentrates for use in soft drink manufacture remains a technical problem. To explore sensory quantifications, a comparison between descriptive analysis (free choice profiling) and ratio scaling strategies was effected. This employed 20 assessors, and a range of commercial black-currant drinks and model product formulations. Free choice profiling yielded product clusters in commercial drinks, but not for formulated drinks. Few descriptors were significant in discriminating samples of the latter group. In addition, assessors were not consistent in quantifying attributes. In contrast, magnitude estimation of the single attribute, overall flavor intensity, produced data which after statistical treatment showed that assessors were able to resolve differences clearly. It was concluded ratio scaling of a single complex attribute had provided a better quantification of flavor character than line scaling of multiple simple attributes.

Notes: In 2 separate studies, 6 rice and 6 dry-cured ham samples were tasted by 2 sets of consumers. The consumers were asked about their hedonic evaluation and invited to comment on the weak and strong points of food samples. The frequencies of quoted terms were analyzed by correspondence analysis (CA). A trained panel carried out the sample profiles. Hedonic scores were linked to objective assessment using the preference mapping (PM). Figures from CA and PM showed similar proximity between samples in both studies. The descriptive vocabulary used by trained assessors and consumers contained both similarities and differences. In the rice study, the trained panel described Basmati with the terms ‘little elastic’, ‘long grain’ and ‘brioche flavor’, while consumers used ‘aromatic’, ‘long grain’, ‘white color’ and ‘good texture’. In the dry-cured ham study, Iberian and Corsican samples were described by ‘rancid’, ‘blue cheese’, ‘mushroom’, ‘bitter’ and 'sweet’ attributes while consumers only used ‘too fatty’, ‘bad taste’ and 'strange’ terms. Trained assessors stressed the greatest sensory differences while consumers focused on salient popular and unpopular traits. Weak/strong points analysis was efficient to show the level of acceptability by the number of strong points attributed to the samples and the main reasons for acceptability or rejection.

Notes: The change in flavor produced by food and wine interactions was explored using descriptive analysis of Hollandaise sauce prepared with two levels of butter and three wines: a Chardonnay which was unoaked, acidified with 1.5 g/L citric acid or aged in oak for one year. To measure the effect of the sauce on wine flavor, the intensity of citrus, buttery, and toasted flavor by mouth and of sourness and bitterness was rated in each wine before and after each sauce was tasted. In a second testing series, lemon, brothy and creamy-butter flavor by mouth and creamy mouthfeel were rated for each sauce before and after tasting each wine. The effect of Hollandaise sauce on wine flavor was greater than the effect of wines on sauce flavor, with the higher fat sauce having a slightly larger effect overall. Sour and bitter flavors of the wines decreased in intensity after Hollandaise sauce was tasted, while the buttery flavor by mouth increased. The toasted flavor decreased significantly in the oaked wine after the sauce had been tasted, while citrus flavor was decreased only for the unoaked wine.

Notes: The suitability of stevioside as a sweetener in peach juice was investigated. Comparison between stevioside and sucrose in terms of sweetness, sweet and bitter aftertastes were determined both in water and peach juice. The results demonstrated that 160 mg/L of stevioside may replace 34 g/L of sucrose in juice, with a 25% decrease in calories, without affecting the sensory characteristics of the product. Synergistic and inhibitory effects between sucrose and stevioside were also monitored at different stevioside concentration. A new juice formulation sweetened with a binary mixture of stevioside (160 mg/L) and sucrose (56 g/L) was not significantly different in terms of desirability from a reference product sweetened with 9% sucrose.

Notes: Visual haze detection thresholds were assessed in thirty panelists by two methods: the ascending method of limits and a transformed staircase procedure (UDTR, from Wetherill and Levitt 1965). The 3AFC test was used as the response procedure for both methods. Experimental samples consisted of an apple juice simulation (water with food coloring). Haze was added to the samples using formazin, and was calibrated to eleven levels ranging from 0.75–13.30NTU. Haze detection thresholds under store-like conditions (3.55 ± 0.57 [mean ± S.E.] and 3.16 ± 0.50 NTU by the two methods, respectively) were higher than those found previously under more controlled viewing conditions. No differences were found between methods, genders, or order of method presentation (p 〉 0.05); a practice effect showed a slight improvement in detection thresholds between sessions (p= 0.05). Nonparametric tests confirmed the similarities in the threshold estimates from the two methods. The two methods estimated visual haze detection thresholds equally well. However, the ascending method of limits may be preferred method due to the shorter time involved in administration.

Notes: Diverse food choices and preferences are commonly observed between consumers cross-culturally, however, many aspects of these behavioral differences are not yet fully understood. In order to investigate cross-cultural texture preferences, six extruded snack samples, manufactured under different processing conditions to represent a range of textural characteristics were characterized by a trained panel using descriptive sensory analysis. In parallel, thirty-eight naive European-Origin and thirty-seven naive Chinese-Origin Australian consumers (t = 75) rated their preference for the snacks. The snacks were not representative of any snacks on the market and thus represented a “ novel” product in both cultures. Additionally, consumers answered a simple questionnaire and completed the food neophobia scale. Results of descriptive analysis indicated significant differences (p≤0.01) between the samples for 13 out of 15 descriptive attributes but no significant differences in preference were found between European-origin and Chinese-origin consumers. However, overall analysis of mean effects indicated that Chinese-origin consumers rated samples significantly higher than European-origin consumers (p≤0.05), suggesting a cultural bias in the use of line scales. Gender did not influence texture preference, however, age significantly influenced preference for three of the samples (p≤0.05) and analysis of mean effects also indicated differences in consumers’ ratings which were related to age. Food neophobia classification did not influence preference, although many more Chinese-origin consumers (28) were classified as neophobic than were European-origin consumers (11).

Notes: Although expert assessment of food characteristics is recognized as a key step in product development, the use of consumer based measurements is sometimes recommended as an equivalent to the experts. From cognitive psychology, support of the role of perceptual learning is found in some instances, although this could not be relevant in others. To address this point performance analysis of experts and untrained panelists in cheese texture evaluation was carried out. Neither the untrained panelists nor the experts were familiar with either the scales or the kind of cheese. The same Cheddar cheese was given to 44 untrained subjects in three trials to assess hardness. The results showed that their judgment has a 29% average random error variance; the interrater reliability being low. The same experiment gave a random error variance of 2% for three highly skilled judges (experts). The difference in variance was linked to training. Untrained panelists also showed an adaptation error. Nevertheless, there was no significant difference between the average ratings of both groups, whether untrained or experts.

Notes: Previous experiments have shown that the same-different test, because of its more suitable cognitive strategy and lower memory requirements, is a more powerful and sensitive alternative to the triangle and duo-trio tests. This project describes an experiment conducted in order to investigate ways to improve further the performance of the same-different test. Three protocols were compared using orange flavored beverages and 24 judges: the same-different method, the triangle test and the dual-pair paradigm. The latter protocol could improve the same-different's performance by preventing the spontaneous variations of the judges’τ criterion. While no significant differences were detected among the d’ values obtained with each procedure, a trend was observed for the same-different and dual-pair test to be slightly more sensitive (higher d’ values) than the triangle test. Since the same-different test is statistically more powerful, it is a preferable choice over the triangle, duo-trio and dual-pair tests.

Notes: The most widely used scale for assessing food liking or disliking is the 9-pt hedonic scale. Unfortunately, this affective scale suffers from problems related to unequal scale intervals and the underuse of end categories, which results in a reduced ability to differentiate among extremely well liked or extremely disliked foods. Magnitude estimation avoids these problems while enabling ratio statements to be made about the data. However, it does not provide absolute ratings of liking/disliking and can be difficult for some consumers to use. We report here on the development of a labeled affective magnitude scale (LAM) scale that has advantages over both the 9-pt hedonic scale and magnitude estimation. Forty-four semantic labels were scaled for their affective meaning by subjects using modulus-free magnitude estimation. The geometric mean magnitude estimates obtained for each semantic label were used to construct a series of labeled affective magnitude scales by spacing the labels along a visual analogue scale according to their obtained semantic values. Reliability and sensitivity studies were conducted to assess the effects of alternative semantic and numeric labels. The results of these studies led to the choice of a scale format that uses verbal labels that are consistent with the 9-pt hedonic scale. The labeled affective magnitude (LAM) scale was compared to the hedonic scale and magnitude estimation in several food preference and acceptability tests. The LAM was shown to have equal reliability and sensitivity to the hedonic scale, provided somewhat greater discrimination among highly liked foods, and resulted in data that were similar to magnitude estimation in terms of the obtained ratios among rated stimuli. The LAM scale was also judged by consumers to be as easy to use as the 9-pt hedonic scale and significantly less difficult than magnitude estimation.

Notes: Contextual shifts were observed for sweetness of a fruit beverage and for estimated tactile roughness of sandpapers. Midrange stimuli were judged to be less intense in the context of stronger items and more intense in the context of weaker items, a contrast effect. The use of a reference standard decreased the size of the contrast shift for the labeled magnitude scale but not for magnitude estimation.