ALBERT

Notes: The purpose of the automatic gain control in seismic amplifiers is to balance the slow decrease of the signal in such a manner that its energy does not exceed the capacity of the recording system. At the same time the interesting seismic content of the signal has to be preserved as undistortedly as possible. At first, the technical data of AGC circuits are calculated. The characteristic curves of circuits with one, two, and three time constants are computed. In circuits with two and more time constants an oscillating of the AGC is possible. In order to guarantee aperiodic operation, the ratio of the time constants must not fall below a certain value. As long as these technical conditions are complied with, the free choice of the largest time constant remains open and can be accommodated to the geophysical conditions.From the endeavour to balance the slow decrease of the signal as well as possible, an upper limit for the choice of the time constants can be derived. A lower limit is obtained from the condition that the seismic content of the signal has to be preserved. The determinant time constant should lie between the two limits and differ from them as much as possible.Finally, the problem of the amplifier “squeezed” by energy pulses is touched.

Notes: Book Review in This Article:P. F. Shokin, Gravimetry (Apparatus and Methods for Measuring Gravity)

Notes: The paper deals with quantitative seismic measurements near underwater explosions. The blastings were carried out in an artificial small pond, the records were taken in adits, situated vertically below the charge. The range of charges extended from one detonator to 200 g of Ammon-Gelit explosive.Conventional seismic scaling by comparing amplitude and size of charge does not yield a simple power law, the exponent being larger for smaller charges and vice versa. This result is due to the different frequency-spectra of the seismic pulses, as shown by harmonic analysis. In contrast to this, the seismic energy as calculated from the records is directly proportional to the size of charge over the whole range.During the Lago Lagorai experiments in 1962 some quantitative seismic measurements near the shot point were also carried out. The relevant results are compared with the preceding ones and some differences are discussed.Some conclusions can be drawn:〈list xml:id="l1" style="custom"〉1The normal methodes, investigating the amplitude only, gives in many cases no clear description; this is especially true for nearby measurements with widely varying frequencies. Therefore it is suggested to extend conventional seismic scaling by including information on the frequency-spectrum and the kinetic energy of the seismic signal.2In order to get clear experimental data for theoretical investigations, it is necessary to extend the recording over a half-space, i.e. in adits or boreholes.3Influences of shape and size of the lake, in which the shots are fired, should be taken into account, too.

Notes: The magnitude of the streaming potential due to the passage of a liquid through a porous medium is examined, under conditions similar to those found in an aquifer under the action of a pumping well. Three models simulate flow in channels, conduits, and unconfined aquifers for several grain sizes of sands and for several resistivities of fluids. The ratio of the streaming potential to the pressure difference is constant for a selected sand and fluid, decreases as grain size increases, is essentially independent of the geometry of the flow, increases slightly as the permeability decreases, and decreases as the salt concentration increases. Extremely low streaming potentials can be expected near a pumping well.

Notes: Book received in this Articles:P. E. Potter and F. J. Pettijohn, Paleoccurrents and Basin Analysis

Notes: Book Review in This Article:Robert L. Miller and James Steven KahnYe. P. Fedorov, Nutation and Forced Motion of the Earth's Pole. Translated from the Russian by Bertha Swirles Jeffreys, Foreword by Sir Harold Jeffreys.

Notes: Case history of the use of fan filtering for improving reflection continuity without destroying their character. The field technique is described: wide-band, large dynamical range recording with a programmed gain control and a very slow A.G.C., small distance between trace centers, high cutoff wave-number.Although the total amount of mixing due to fan filtering is rather high, a broad spectrum was obtained and inverse convolution filtering was used to improve trace resolution.

Notes: Graticules are known for the calculation of the magnetic field of homogeneously magnetized “two-dimensional” structures. For bodies whose lateral dimensions are comparable with the dimensions of the cross section and/or the distance between the point of observation and the structure, these graticules allow an approximative computation of the field in the plane of symmetry only. The degree of approximation can be improved by means of end corrections, but the amount of work involved increases rapidly. Moreover, even with end corrections the applicability of the graticules is still restricted to cases of rather simple geometry.In this paper, a set of graticules is proposed which already incorporates all end corrections. The set consists of three graticules, and it can be shown that at any point of observation lying outside the body each graticule needs be applied once only in order to calculate any component of the magnetic field produced by a homogeneously magnetized cylinder of arbitrary cross section, finite lateral extension and arbitrary spatial orientation.Curves and tables have been prepared, which allow the construction of the graticules under consideration. The application is illustrated by a hypothetical example. Possibilities for further improvements of the method are discussed.

Notes: By this method an approximation of gravity-anomaly of an inhomogeneous mass with any form is calculated. The mass is inbedded in a homogeneous medium. The density of the medium differs from the density-distribution of the mass.

Notes: Book Review in this Article:H. Israel and A. Krebs, Nuclear Radiation in GeophysicsB. A. Tkhostov, Initial Rock Pressures in Oil and Gas DepositsJohn S. Steinhart and Robert P. Meyer, Explosion Studies of Continental Structure

Notes: Pour caractériser les anomalies de la carte initiate et de la carte transformeé, on définit des indices de netteté désingés respectivement par I0 et I et on étudie le rapport I/I0 pour diverses formules appliquées à trois anomalies typiques (sphère, anticlinal, faille). Les courbes obtenues permettent d'introduire, par analogie avec les circuits électriques, des notions telles que profondeur de coupure et pente.

Notes: In the case where a medium of velocity α1 is underlain by a medium of higher velocity α2, no propagation of compressional elastic wave energy into the lower medium takes place at angles of incidence exceeding a certain critical value. This so-called critical angle –which is a measure of the actual velocity-contrast –is furthermore marked by a sharp increase in the amount of reflected compressional energy. An investigation has been made to find out whether this critical-angle effect might be usable as a velocity-contrast indicator in seismic exploration.Model experiments confirmed the expectation that this effect should be manifest at the surface under ideal conditions.Two small-scale field set-ups showed that the effect is actually measurable in the field (in one case after applying corrections for planting variations).Finally a seismic line along the shore of the North Sea provided the data for contrast analysis over a considerable distance along the base of the Tertiary. Comparison of the measured changes in contrast and subcrop velocities obtained at those locations where subsurface data from independent sources were available, showed good agreement.It is concluded that critical-angle shooting may be used to indicate subcrop changes along a reflector, or even to obtain the same sub-stratum velocity as is sought in conventional refraction work, at considerably shorter operating distances.

Notes: Nach einer kurzen Einführung über das Prinzip der Vibratortechnik werden Ergebnisse vibratorseismischer Arbeiten auf Platten (Eis, Betonplatten, Straßendecken) mitgeteilt. Der Auswertung wurden Biegewellen zugrunde gelegt und die ermittelten experimentellen Ergebnisse mit theoretischen Dispersionskurven verglichen.

Notes: Using optimum filter theory as a starting point, we describe a method for the design of practical multi-trace seismic data processing systems. We assume the inputs to be the superposition of signal, coherent noise, and incoherent noise. The signal and coherent noise moveouts are described statistically by their probability densities. Our approach is to split the system into two stages. The first stage achieves optimum noise suppression but distorts the signal. The signal distortion is reduced in the second stage by an optimum finite memory inverse filter.The system that is obtained using our method of design depends upon the form of the probability density functions. We show two examples, ghost suppression and velocity filtering. In ghost suppression we choose a model with moveouts known exactly, which corresponds to delta functions for the probability densities. In velocity filtering the signal and coherent noise moveouts are equally probable within non-overlapping ranges.The resulting system in each case is both simple and effective. In ghost suppression a simple shift and subtract cancels the coherent noise. The signal distortion is reduced by an inverse filter. The velocity filter system consists of differentiated moving averages applied to each trace, followed by a 90° phase shift and a low pass filter.

Notes: A graphical method of interpreting refraction data is presented based upon wave front construction in which different overburden velocity distributions can be used. The wave fronts are constructed with the aid of an Isochron Chart. By using two or more Isochron Charts, the effect of velocity variations above the refractor of interest can be allowed for.

Notes: This study is an attempt to find a phenomenological model which will behave in a manner similar to that of common earth materials in regard to the dependence of attenuation and phase velocity on frequency.An analysis of two commonly employed rheological models, Maxwell's and Kelvin-Voigt's and their variants, is presented indicating that these models are too simple to conform phenomenologically to the behavior of rocks. It is shown that a linear combination of the Maxwell and Kelvin-Voigt models, known as the standard linear solid, comes closer to giving an adequate description of the behavior of some earth materials, than either one of the two models.A method of determining the viscoelastic constants of a solid is presented provided that its attenuation and dispersion curves are known. The viscoelastic constants (relaxation times and/or viscosity coefficients) of the solid are determined by superimposing the experimental curves on master curves, and reading the constants off the theoretical curves.An analysis of published experimental data is presented, indicating that the present model is capable of accounting for at least some attenuation and dispersion phenomena.

Notes: Two groups of ewes, each containing single and twin lambs, were folded over a ‘worm-free’ pasture, with a creep provided for the lambs, allowing them to graze ahead of the ewes. The lambs of one group received supplementary feeding. Higher growth rates of the Iambs were recorded than those previously reported by other workers. The growth rates of twin lambs were improved more than those of singles and the lambs receiving supplementary feeding gained at a significantly faster rate than those on pasture only. Faecal egg counts indicated that worm infestation in the lambs was maintained at a very low level.

Notes: Data from an experiment already reported (2) are used to examine a statistical method proposed by Walker et al. (8) for apportioning the nitrogen harvested in grass in a grass/ legume sward to legume, fertilizer and soil. Multiple regressions of the yield of N in the grass (Gn) upon N harvested in the associated legume (Cn) and N applied in fertilizer (Fn) were highly significant; but they were very variable, mainly because of the strong (negative) correlation between Cn and Fn. In some cases the coefficient for clover N was negative, in some cases the coefficient for fertilizer N exceeded unity; and the residual constant varied widely among 4 sets of plots on the same soil. The interpretation of such equations in physical terms is criticized on these grounds. The use of pure grass swards in conjunction with mixed swards gave estimates of the recovery of fertilizer N, and of the transfer of N from clover to grass, which agreed better with other published data than did the coefficients in a multiple regression. A simple regression of the estimate of transferred N in the grass upon the N harvested in the clover yielded a second constant. This constant, which varied considerably from one series of plots to another, is thought to indicate interactions between the various sources of N, which would be attributed to a direct effect of soil N if the multiple regressions were interpreted as Walker et al. suggest.

Notes: Pure swards of S22 Italian ryegrass, H.1 hybrid ryegrass, S170 tall fescue, S48 timothy, S215 meadow fescue and Germinal cocksfoot were each harvested at several stages of maturity during first growth in the spring, and in the subsequent regrowths. Each batch of herbage was fed to sheep in a digestion trial under conditions of voluntary intake. Results from the first growth herbages showed the expected fall in digestibility with increasing maturity. However, the digestibility of S22, H.1, S170 and S48 began to fall well before ear emergence, whereas the digestibility of Germinal fell only slowly up to the time of ear emergence, as had been found previously with S24 and S23 ryegrass and S37 cocksfoot. The rate of fall of digestibility in H.1 and S48 (0.4 units/day) also appeared to be lower than with the perennial ryegrasses and cocksfoot (0.5 units/day). The monthly regrowths within each herbage were of similar digestibility, but the mean digestibility of regrowths differed between herbages, being highest for S215 and lowest for Germinal and S170. The grasses with highest digestibility in the early Spring, in particular S22 ryegrass, were not, however, always the most digestible in the subsequent regrowths. The numbers of sheep fed on each herbage were insufficient to show whether there were significant differences in voluntary intake between different herbage species of the same digestibility. It is suggested that an intake/digestibility relationship, based on data from more animals, should be developed for each herbage species. Only if different relationships are found can it be concluded that factors other than level of digestibility have an effect on intake.

Notes: The productivity and persistence of 27 varieties of herbage plants were compared, following sowing on a blanket peat after ploughing. Yields were estimated from 3–5 cuts per year for 5 growing seasons. The top yields in each year ranged from 2510 lb/ac. in the 5th year when no nitrogenous fertilizer was applied up to 4700 lb/ac. in the 3rd year when given 174 lb N/ac. Such levels are slightly less than half the level expected on lowland, but livestock output on hill land is far lower than on lowland. Varietal differences were significant, with red fescues, especially S59 smooth-stalked meadow grass, S170 tall fescue, S143 cocksfoot, Yorkshire fog and S53 meadow fescue giving top yields and persistence. Aberystwyth varieties were in all cases superior to other varieties. S50 timothy and S23 perennial ryegrass were persistent but production was low. The conclusions are compared with those of other investigators.

Notes: The traditional method of calculating field output by the utilized-starch-equivalent (U.S.E.) system is compared with a recommended simpler and quicker method. The concept of calculating a U.S.E. factor is introduced and forms the basis for the new method. A monthly U.S.E. factor is used, in conjunction with monthly cow-day (CD.) records to calculate U.S.E. Savings of at least 50% may be expected. Agreement between the two methods is very close and the more seasonal nature of the calculation for sheep and non-milking cattle under the new method may be preferable.

Notes: Normally only operational checks are made on geophones in the field because of the lack of suitable test equipment. The test method described here was developed to enable accurate (better than 1 %) measurements to be made, in the field, of all geophones in common use which have natural frequencies of i c/s or greater.The portable field instrument is simple to operate and can be used to test refraction and reflection geophones, either singly or in series strings.

Notes: An analytical expression for the time-distance curve of seismic waves travelling in a medium consisting of intrinsically anisotropic layers with arbitrarily dipping plane interfaces can be given in terms of the “co-ordinates” of the interfaces (length h of the perpendicular from the shotpoint to the interface, strike ν and dip α of the interface) if for each layer the velocity is given as a function of the orientation of the wave normal. The interpretation of the time-distance curve is understood as the inverse process, namely finding an expression for the co-ordinates in terms of some characteristics of the time-distance curve, e.g. intercept times and apparent velocities. In addition, it is useful to know where the “limiting ray”, which is the ray connecting shotpoint and last geophone, enters and leaves a specific layer, for it is only on the medium between these two points that information can be obtained by interpretation. As ray and wave normal do not generally coincide in anisotropic media, the location of these points cannot be calculated from the co-ordinates and the direction of the wave normal without recourse to the functional dependence between the directions of ray and wave normal.An analytical solution of this problem would involve the solution of a number of equations, implicitly containing several parameters. Successive approximation would be rather cumbersome. Instead, a graphical method is proposed which yields all pertinent information without calculation.

Notes: This article deals with the effect that the Königsberger ratio, the ratio of remanent to induced magnetization, has in modifying the dipping-dyke equation. Many reversed dykes are found on aeromagnetic maps and their presence indicates that remanent magnetism must often play a significant part in the magnetic expression of normally-polarized dykes. The methods for the measurement of remanent magnetization and susceptibility (k) are outlined, and the relationship between k and volume % magnetite (V) is discussed. It is proposed that a good approximation is k= 0.15 (x−1 - x), where x=1-V/100. The general equation for the dipping dyke, which includes the contribution of remanent magnetization, is given. A method of obtaining k from the magnetic map is also derived.

Notes: In 1960 spring-born calves were reared indoors or at pasture on 3 dairy farms near Hurley. In the following year the experiment was repeated on 3 farms in the nortli-east and on 2 in the south-west of England.Several calves died, and this may have been because of inadequate milk feeding. Generally, however, the growth of calves reared at pasture was comparable with that of animals reared indoors. Tfie use of grass enabled substantial savings to be made in the amount of concentrate feedingstuffs and hay fed.

Notes: Digestibility data are presented on the following; Andropogon gayanus hay and bush foggage, Arachis hypogoea (groundnut) haulms, Glycine max (soya-bean) hay. Sorghum vulgare (sorghum) leaves and hay, Stizolobium sp. (velvet bean) hay, Vigna sinensis (cowpea) hay and haulms, and S. vnlgare/Stizolobium sp. mixture. The results are discussed from the agronomic aspect.

Notes: Two systems of recording the output of grass fields—by cow-days (CD.) and by utilized starch equivalent (U.S.E.)—were compared with field measurements of the dry matter and digestible matter consumed over a period of two years.On one farm, each recording system was positively correlated with both the amount of dry matter and the amount of digestible matter consumed from individual fields by grazing cows. Consequently, the two systems reflected equally well the total quantity of utilized herbage and its quality. This was explained by a highly significant correlation between the two recording systems. The same correlation between the two recording systems existed on 20 other farms.It was concluded that the C.D. and the U.S.E. systems gave equally reliable results when assessing field output within dairy farms. Because C.D. can be determined with greater ease they should be used instead of the U.S.E. system. However, the U.S.E. system is still advocated for assessing grass utilization for animal production on a farm basis, since it indicates the level of efficiency which farmers achieve in using their grass.

Notes: An investigation into the merits of intensive rotational grazing or paddock grazing was started in 1960. The experiment covered 40 acres, half of which was divided into 20 single-acre paddocks and the other half into 2 fields of 9 and 11 acres, respectively. Two groups of carefully paired cows were used to measure the output of milk per acre. Surplus grass was used for drystock and for conservation. The final output was expressed in terms of U.S.E. per acre, which was computed from the records of milk production, livestock maintenance and fattening and grass cut for conservation. The following conclusions seem reasonable: (a) Where the stocking rate is the same under both systems and the grass supply exceeds the animals' appetites, very little difference in terms of milk yield per acre will be found between intensive rotational grazing and lax rotational grazing over the grazing season; (b) Where, because of heavier stocking or a poorer growth of grass, the animals' appetites begin to exceed the grass supply, the intensive system of rotational grazing will be able to carry the stock for a longer period and consequently will give a greater output of milk per acre; (c) Intensive rotational grazing gives greater opportunity for taking off surplus grass for dryslock or for conservation.

Notes: A comparison of non-mat and mat ecotypes of three reseeded hill swards showed that mat pasture soil was characterized by relatively high C/N ratios, low available nutrient status, low burrowing earthworm biomass, and low soil microbial activity (determined as CO2 evolution).A replicated trial was laid out on a uniform mat area of one of these swards (Ciderhouse Hill) and lime and fertilizer treatments were applied in two successive seasons. Lime treatment reduced mat weight, increased the proportion of ‘sown’ grasses in the sward and stimulated soil microbial activity, Initially, burrowing earthworm biomass was inhibited by lime; but, after an interval of four years, a positive response was noted at the lower treatment level. Sodium nitrate interacted with lime to increase soil microbial activity. Soil cellulolytic activity was increased by nitrate and phosphate treatments. The level of soil moisture in the field at the time of soil sampling appeared to influence soil microbial activity measured under standard conditions in the laboratory: high rainfall tended to reduce microbial activity. The significance of these findings and the infiuence of nutritional and climatic factors on sward reversion and mat formation are discussed.

Notes: The sheep grazing intensity and herbage intake on 3 high-level grasslands above 2250 ft were investigated. The seasonal intake, which varied from 450 to 700 lb dry matter/acre, was obtained by the yield-difference method, using cages moved monthly.

Notes: Leaf-area index was increased by nitrogen application, but the increase was restricted by frequent cutting, which limited the incidence of high leaf-area indices. Timothy swards had higher leaf-area indices than meadow-fescue swards between April and mid-July, the period in which maximum values were recorded. N significantly increased the leaf area per g of leaf (leaf-area/leaf-weight ratio) at the beginning of the experiment, but not thereafter; the effect of cutting on this ratio varied with the date of cutting. Leaf areas per g of leaf were similar for the 2 species at the beginning and end of the experiment, but in mid-summer values for timothy increased whilst those for meadow fescue decreased. The relationship between leaf-area index and yield of dry matter is discussed.

Notes: Book reviewed in this article:CUNNINGHAM LABORATORY, C.S.I.R.O., AUSTRALIA. Some concepts and methods in sub–tropical pasture researchEDWARDS, C. A., HEATH, G. W. The principles of agricultural entomology.MINISTRY OF AGRICULTURE, FISHERIES AND FOOD, ENGLAND AND WALES. Hay: quality and feeding.

Notes: Studies on height/weight relationship of the key grass species of Western Rajasthan ranges, India, were undertaken so as to form concepts which will guide the assessnient of the extent of their utilization by the livestock. Regression studies of the data obtained indicated that the relationship between the percentage of height clipped and the percentage of weight removed is quadratic. A graph has been drawn for each of the 5 species to relate the percentage of height removed with the percentage of weight utilized. The studies have shown that the weight distribution in respect of height is different in different species.

Notes: The dry-matter intake of silage was increased when the silage had a higher dry-matter content and when the time of access to the silage was increased from 3 to 24 h. Concentrate supplementation had a greater influence in depressing the intake of hay than that of silage. Only a small difference was observed in the replacement of hay by concentrates when the concentrates were given with two hays of different dry-matter digestibility. Concentrates with a relatively high protein content depressed roughage intake to a lesser extent than concentrates with a low protein content.

Notes: Book reviewed in this article:McILROY, R. J. An introduction to tropical grassland husbandry.MINISTRY OF AGRICULTURE FISHERIES AND FOOD. Bulletin 195: Fertilizers for the farm

Notes: An experiment on the prevention of hypomagnesaemic tetany by foliar application of calcined magnesite was carried out with the dairy herd of Greenmount Agricultural College. Hypomagnesaemia and tetany were prevented by‘dusting’ pasture with calcined magnesite at the rate of 28 lb per acre just before grazing, whereas hypomagnesaemia and cases of tetany (including one death) occurred when the animals were grazing pasture which had not been dusted.

Notes: Populations of Lolium spp., Dacrylis spp., and Phleum, each based on two or more cultivars, were subjected to three managements and iwo nitrogen levels. Rapid changes i n population structure occurred in response lo agronomic selection pressures and some cultivars were eliminated from the swards in less than four years, even though they were able to persist for longer periods when sown separately. The frequency and method of defoliation, time of nitrogen application, and edaphic factors produced changes i n the proportion of the cultivar subgroups in the populations, and there were indications of differential survival within cultivars. The results are discussed in relation to the utilization of cultivars in mixtures and the selective action of biotic and edaphic factors.

Notes: The release of the plant-cell juices is a prerequisite for a lactic-acid fermentation in silage. Investigations with plant material at different moisture contents have indicated that above about 2 g water per g dry matter sufficient juice is released from properly ensiled material to permit the onset of fermentation; below this moisture content lactic-acid production is delayed, if not prevented.When material of suitable moisture content is ensiled at a temperature of 25°C, the onset of fermentation is somewhat slower than at 40°C. However, within these limits, the temperature is not critical, provided that the silage is completely sealed to exclude air. The infiltration of even small amounts of fresh air delays the release of the juices and, especially at the lower temperatures, often results in an undesirable fermentation.A number of miscellaneous treatments, designed to hasten the release of the juices, failed to show any advantages in small-scale tests.

Notes: The two years' experiments described compared the growth of suckling lambs on ‘long’ and ‘short’ ryegrass swards. The animals were carried at a moderate stocking rate. Differences in sward height were established before grazing began and were maintained throughout each season. There were no significant differences in lamb growth between treatments. The structures of the swards are discussed in relation to the results, and the possible effect of differences in parasitic infestation on ‘long’ and ‘short’ swards is considered.

Notes: Using ryegrass and lucerne silages, investigations were made into the relationship between plant-cell breakdown, as evidenced by a collapse of the silage mass and by an increase in its electrical conductivity, and the initiation of lactic-acid production. Changes in the water activity of the juices available as a medium for the silage bacteria were also examined. It has been shown that cell breakdown and the resultant release of the plant juices Is a necessary pre-requisite for the production of significant amounts of lactic acid during ensilage. The investigation also confirms that the complete exclusion of fresh air from the silage mass can usually be expected to result in cell breakdown within a few hours.

Notes: There was a significant reduction in the seed yield of S26 cocksfoot in the first harvest year following undersowing in oats. Yields were markedly improved, however, by the application of extra nitro-chalk in spring, by using a partial cover crop and by cutting the oats for silage.Over three harvest years the financial returns were very similar for all treatments studied.

Notes: Book reviews in this article:CLARKE, H. G. Commercial sheep management.VOISIN, A. Grass tetany.WALSH, A. Profitable meat production.

Notes: This paper deals with transient response of resistive formations to pulse sources. Computation of solutions of equations such as:〈displayedItem type="mathematics" xml:id="m1"〉1〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR325:GPR_325_m1"/〉is linked to computation of solutions of equations such as:〈displayedItem type="mathematics" xml:id="m2"〉2〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR325:GPR_325_m2"/〉It can be used in the case where several media exist, the conductivities of which are σ1 σ2.The method consists in establishing a correspondence between the case to be dealt with and a fictitious region of space with the same interfaces, in which the propagation of a disturbance obeys Equation (2).Velocities C1 C2. are related to conductivities by the condition〈displayedItem type="mathematics" xml:id="m3"〉3〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR325:GPR_325_m3"/〉At the interfaces, the distribution of incident energy between transmitted and reflected energy is related to the ratio of characteristic impedances, i.e.〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR325:GPR_325_mu1"/〉in the real case (ω is the angular frequency) and C1/C2 in the fictitious case.These ratios are the same because of Equation (3).Time variation g(θ) of solution of (1) in a given point is computed from time variation of solution of (2) at the same point by means of the transformation〈displayedItem type="mathematics" xml:id="m4"〉4〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR325:GPR_325_m4"/〉(in which τ is the actual time and T the time unit).Equation (4) originates from a formula of symbolic calculus, that allows the Laplace transform of F(Vp) to be calculated from the known Laplace transform of F(p). This correspondence is the one that allows passage from 〈inlineGraphic alt="inline image" href="urn:x-wiley:00168025:GPR325:GPR_325_mu2" location="equation/GPR_325_mu2.gif"/〉 in (1) to 〈inlineGraphic alt="inline image" href="urn:x-wiley:00168025:GPR325:GPR_325_mu3" location="equation/GPR_325_mu3.gif"/〉 in (2)Equation (4) becomes considerably simpler when the response 〈inlineGraphic alt="inline image" href="urn:x-wiley:00168025:GPR325:GPR_325_mu4" location="equation/GPR_325_mu4.gif"/〉 to the unit impulse consists (as happens most often) of the sum of a finite or infinite number of pulses 〈inlineGraphic alt="inline image" href="urn:x-wiley:00168025:GPR325:GPR_325_mu5" location="equation/GPR_325_mu5.gif"/〉 The results is then a sum of functions such as:〈displayedItem type="mathematics" xml:id="mu6" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00168025:GPR325:GPR_325_mu6"/〉Hence, this procedure appears as an extension to systems that obey Equation (1) of the image theory very often used when Equation (2) is applied.

Notes: The exact responses of plane interfaces to incident spherical compressional waves are calculated by an electronic computer. The reflected part of the response is shown for various positions of the ‘shot’ and of the ‘receiver’ as well as for various velocity contrasts. This makes it possible to study some features of the reflection process, especially the behaviour beyond the critical angle.

Notes: The problem of three-dimensional migration is solved for arbitrary, three-dimensional, continuously differentiable velocity functions v=v (x4) by means of series.The derived formulae are applied to numerical examples.The possibility of approximating real, discontinuous velocity distributions by continuous functions is mentioned and illustrated by an example.The application of electronic computers, which is necessary due to the complexity of the formulas, is discussed.

Notes: Determinations of the in vitro digestibilities of leaf-blade, leaf-sheath and stem fractions of the grasses cocksfoot, perennial ryegrass, timothy and tall fescue and of the leaves and stems of lucerne and sainfoin have shown that all parts of the plant have a high digestibility at early stages of growth. With increasing maturity, however, the digestibility of the stem falls off at a much faster rate than that of the leaf; in grasses, leaf-sheath digestibility declines at an intermediate rate. The decline of digestibility is associated with a reduction in the content of water-soluble and protein constituents in the plant, and with a reduction in the digestibility of fibre. This may provide a biochemical basis for the selection of forage plants of high digestibility in plant-breeding studies.

Notes: The effects of (2–chloroethyl) trimethyIammonium chloride (CCC) on inflorescence production and culm length in seedlings of Aberystwyth S51 timothy (Phleum pratense L.) are described. Concentrations of CCC ranging from molar to 0.01 molar were applied as a soil drench at a rate of 75 ml/sq. ft to plants at the 3rd, 6th or 8th leaf stage. All treatments reduced the culm length at heading, maximum effect being obtained from those given at the earliest growth stages. The number of heads per plant and the total head-length per plant increased with treatment, showing a maximum after molar treatments at the 6th or 8th leaf stages. Mean head-length remained relatively constant. The results are discussed in relation to seed production problems and the questions to be answered prior to field-scale treatment are outlined.

Notes: Leaf and tiller development along the main shoot of cocksfoot, ryegrass, timothy, Hordeum bulbosum, meadow fescue, S170 tall fescue and an Algerian tall fescue are described. Comparisons between plants grown at two levels of applied nitrogen, and in a heated and an unheated glasshouse, from January to April, 1961, showed that timothy, cocksfoot and, to a lesser extent, H. bulbosum and ryegrass, generally developed leaves faster than the fescues. Numbers of live leaves per shoot, and numbers of actively-elongating leaves per shoot declined in a similar varietal order. Despite this, the large leaves of the fescues resulted in their having a leaf area per main shoot equal to, or exceeding that of, the other grasses for most of the experiment. In general, rate of leaf appearance, number of live leaves, number of actively-elongating leaves and leaf length were increased by a high level of N and high temperature, but high tesnperature reduced leaf width and, in some instances, tiller numbers.

Notes: Extensive replicated plot experiments were carried out at Henley Manor Farm from 1956–1961 to obtain accurate measurements of herbage production and response to nitrogenous fertilizers under West of England conditions. 356 plots were used; use of the herbage by both cutting and grazing was studied. The principal results are: Grass/ clover swards (containing approx. 35% clover) grown without nitrogenous fertilizer averaged 75 cwt dry matter per acre per annum. Application of nitro-chalk to initially grass/clover swards reduced the clover content of the herbage. About 133 lb N/annum was required by an all-grass sward to equal the production of a grass/clover sward without N. Attempts to increase production of grass/clover swards by using N for early growth and relying on clover for mid-season growth were unsuccessful in 2 out of 3 years. Swards (initially grass/clover) gave significant increases in total dry-matter production from regular use of the lowest level of N (26.0 or 34.7 lb N/acre/cut or graze) in 44 out of 49 cases. Extremely high yields were obtained from the heaviest use of N (104.2 lb N/acre/silage cut). 52.1 lb N/acre/cut or graze was the optimum rate of application on ail-grass and grass/clover swards. Up to about 350 lb N/acre/annum the dosage-response curve was very nearly straight for all-grass and grass/clover swards. On the grazed plots herbage left ungrazed amounted on average to only 6% of the total. The health of all stock on the high nitrogen plots (as well as all others) was excellent.

Notes: Assessments of animal preference (measured as mean % herbage removed) were made on varieties of cocksfoot in Yorkshire and in Scotland, and parallel chemical analyses were carried out. A similar range of varieties were examined at progressive stages of spring growth at Cambridge. In vitro digestibility tests were made also. In the Yorkshire trials, a significant positive relationship was established between soluble carbohydrates and animal preference and a negative correlation between fibre and animal preference. In Scotland, the relationship between soluble carbohydrate and animal preference was less pronounced. Animal preference in the spring was for the early varieties which have thick and succulent stems up to the stage of ear emergence. In the aftermath animal preferences were less marked.In trials at Cambridge, the early varieties, notably Scotia, were higher than the late varieties both in digestibility and in soluble carbohydrates. This tendency was also present in Scotland but was less pronounced.

Notes: Details are given of the system of grassland management used on the farm of the Hannah Dairy Research Institute in the 5-year period 1958–62, when the aim was to inerease production economically by achieving a balance between the use of grass, grassland conservation products, home-grown cereals and the minimum amount of purchased feeds.Over the period the number of cows and lst-calf heifers increased from 50 to 53, while the total annual milk production increased from 41,000 to 50,000 gal. The yield of milk increased from 820 to 945 gal. per cow, and from 300 to 380 gal. per acre. Concentrate usage declined from 2.5 to 1.8 lb per gal.The margin of milk sales less purchased feed rose from £111 to £129 per cow in the 5 years and the net output averaged £59 per acre. The health of the stock was excellent.

Notes: When light dressings of 0·75, 1·50 and 2·25 cwt muriate of potash per acre (60% K2O) were applied in autumn and spring to swards receiving two levels of sulphate of ammonia, 30 or 60 lb N/acre, and kieserite (29% MgO) at 0, 4 or 12 cwt/acre, magnesium content was reduced as the level of muriate of potash increased. Autumn application resulted in a higher magnesium content, at the expense of the amount of the potash absorbed in the spring herbage. The effects at the lowest levels of application of muriate of potash were slight and became insignificant in later herbage samples.

Notes: During 1959–62 a study was nmdc of the effect or the density of plant population, photoperiod, temperature and light intensity on stolon rornialion, floral induetion, bud expansion and inflorescence development in S184 white clover.The density of the plant population alfected not only stolon and inflorescence formation, but also the root system. The‘open’ sward with about 60 plants per sq. yd gave the highest number of inflorescences per unit area, and al the same time contained few plants with tap roots.White clover had a long-day photoperiodjc requirement, but there was variation between the individual plants in their requirements of daylength, temperature and light intensity.Overwintering did not appear to be essential for floral induction and primordia development. Too low or too high temperatures during the overwintering period appeared, respectively, to delay or stimulate vegetative growth, while both extremes of temperature seemed to delay floral induction and reduce inflorescence formation. A medium range of temperature (40°–55°F) followed by an increasing temperature, daylength and light intensity, appeared to be most satisfactory for primordia initiation and flowering.There is some inter-relation between temperature and light intensity, but light intensity stimulates vegetative growth and development of the primordia, as well as being essential for the formation of numerous inflorescences.

Notes: The mean yields of 4 varieties of lucerne were compared under 5 methods of growing: broadcast with and without grass; drills 2 ft apart; alternate lucerne/grass drills 1 ft apart; spaced plants. One cut was harvested in the sowing year and 3 cuts a year for the next 3 years.The alternate lucerne/grass drills yielded 20% less dry matter than the comparable broadcast plots. Broadcasting and sowing in alternate drills had the same effect on the pattern of lucerne/grass competition. The meadow fescue companion produced its highest yield at the first cut and there was a marked drop during each year and from year to year. There was little evidence of nitrogen transfer from the lucerne to the grass.

Notes: Perennial ryegrass and meadow fescue were grown alone and in association in field plots, to gain an idea of the nature and importance of the competitive interactions between them, and their relative contributions to the yield of the newly-established sward.Experiments over 10 weeks and 9 months both showed that the contribution by fescue to the overall dry-matter yield was severely restricted by perennial ryegrass. There were no deaths of fescue plants during the experimental period (which included an overwintered treatment). The depression in yield was rather a result of a marked decrease in size and weight of the individual plants, brought about by competition for light and nutrients from the faster-growing ryegrass.

Notes: Two levels of nitrogen application (70 and 180 lb per acre per annum) were compared on 6 long-duration leys. The treatments were repeated for periods of up to 4 years on tiie same swards. The higher N dressing produced 2230 lb more dry matter per acre than the low rate, an increase of 28%, and the yield was also more evenly spread throughout the season. There was virtually no clover on the high-N swards. The proportion of clover varied under low N but tended to increase as the season progressed. The sown grasses remained the dominant sward constituents throughout the experiment, and there was no sign of loss of vigour on the high-N swards. Utilized-starch-equivalent outputs were calculated from 3 different swards for 1956–8 and there was a significant positive correlation between the dry-matter yields and utilized-starch-equivalent output of swards.

Notes: Cocksfoot sown late in summer or early in autumn to provide a seed crop the following year generally produces a disappointing yield. The experiments described were set up to study this problem. Seeds of four varieties, American, Danish and two British cocksfoots, were sown at fortnightly intervals during the spring and summer of 1956. The sowings were repeated in 1957 with the addition of Potomac, a bred variety from USA, and an ecotype from Israel.Plants sown after mid-May showed a diminishing capacity to produce panicles the following summer. The last sowing in 1957 caused the weight of green hay per plant in 1958 to be at least 50% below that of the spring-sown plants, and panicle number to drop 60–80%. Sowing after mid-May affected panicle development in the autumn and in the following hay crop. Date of sowing had no effect on mean date of panicle emergence in the following summer. In the populations as a whole, neither the presence nor the number of panicles in the first autumn was related to productivity in the hay stand.

Notes: The effects of sowing from 10 to 50 lb/acre of tall-fescue seed on plant establishment and on the annual and seasonal distribution of DM yield of tall fescue and its companion grasses were measured through two growing seasons. Increasing the seed rate increased plant numbers per unit area and decreased per cent establishment. Adding Scots timothy as a companion grass depressed both plant number and per cent establishment. S37 cocksfoot and New Zealand perennial ryegrass reduced both still further. Total annual dry-matter production was relatively unaffected by varying either the seed rate or the companion grass. The contribution of tall fescue to total production was highest when sown alone and was successively reduced by timothy, perennial ryegrass and cocksfoot. When sown alone there were only slight differences in contribution of tall fescue due to seed rate. With any companion grass the contribution from tall fescue increased with increasing seed rate. Early growth was not reduced by modifying seed rate but was reduced by all the companion grasses. It is concluded that increasing the seed rate of tall fescue above 30 lb is not justified, that Scots timothy can be sown at 3 lb/acre with tall fescue without affecting total production or early growth of the mixture, with the advantages of control of unsown species and improved palatability of the herbage.

Notes: Differences resulting from previous cropping were shown in the yields of the first test crop of rape and also in the second test crop of oats which followed. Rape yields were highly correlated with the yield of the legume crop harvested earlier in the season, the highest residual effect being observed after lucerne, followed by lucerne/grass, red clover/ grass and grass alone, in descending order. The application of nitrogen to the legume and grass swards reduced the yield of oats, the second test crop. Here again, lucerne gave better residual yields than grass.

Notes: Eight lots of seed of S23 perennial ryegrass which had been artificially dried to different moisture levels and stored for 20 years were tested for germinating capacity, and the effects of long-term storage on subsequent plant development were studied. The results of the germination tests indicated a continuation of the downward trend in viability previously reported. Observations on the derived mature plants revealed no difference between lots in general growth habit; a few seedlings showed symptoms of some retardation in growth but most plants manifested the high tillering and prostrate growth typical of S23 perennial ryegrass. Pollen fertility was markedly reduced in 38% of all the plants sampled. The seed-setting capacity was affected to an even greater extent, 44% of the plants giving seed-set values decidedly below those obtained for plants grown from new seed. Where pollen fertility had been much reduced, seed-setting also was usually low, but there were some instances of satisfactory pollen fertility associated with a low seed set.

Notes: Three grazing managements (set stocking, 4-paddock rotation, 8-paddock rotation), each with an undivided lateral creep area, were studied. Each of these managements carried 2 stocking rates (6 ewes and twin lambs per acre, 10 ewes and twin iambs per acre) and the sub-divided managements were grazed at 2 severities of grazing.Stocking rate had a major effect upon the lambs' liveweights but did not significantly affect the ewes’ liveweights. Lambs on set-stocking managements had a significantly higher rate of liveweiglit gain than lambs on managements with sub-divided ewe areas. Under lax grazing, for much of the experimental period, the lambs had a significantly higher rate of liveweight gain and the ewes had significantly higher liveweights than under severe grazing.

Notes: A suggested new method for studying the depth of grass seed germination and emergence is described.

Notes: Book review in this article:WORDEN, A. N. SELLERS, K. C. TRIBE, D. E. Animal health, production and pastureSTAPLEDON, G. [WALLER, R. Ed.] Human ecology.

Notes: The effects of three stocking rates on fat-lamb production were examined. These stocking rates were imposed upon four grazing systems. The grazing managements had no significant1 effects upon the rate of liveweight gain or the total liveweight of lamb produced per acre, nor were the ewes’ liveweights significantly affected. Reasons are suggested. The lambs’ rate of liveweight gain was related negatively and the total liveweight of lamb produced per acre was related positively to stocking rate. The ewes’ liveweights were similarly affected, there being the highest losses of liveweight under the high stocking rate. In all cases significant differences existed between the stocking rates and there was a significant linear relationship between them. It is concluded that high stocking rates are essential to obtain the maximum fat-lamb production on a ‘per acre’ basis.

Notes: An hypothesis relating to the circulation of nitrogen between soil, plants and animals in fertilized grassland is presented. It embodies the results of small-plot experiments and grazing trials on serai grassland in South Africa. Where the value of land is low in comparison with the cost of fertilizer, it is essential that the maximum response be obtained from fertilizer as well as from excretal N. The assumption that 80% of herbage N is returned as excreta, of which 25% is recovered by the grasses in the first season and 25% in the second season, appears to be in accord with liveweight data. Using average values of soil N and fertilizer recovery under local conditions, it is argued that applying 30 lb N per acre (with an initial heavy dressing) should provide higher percentage recoveries of fertilizer N than fixed annual dressings of 60 Ib N per acre. In grazing trials over five years, in which these systems are compared, the apparent recoveries of fertilizer N in animal liveweight were respectively 22.4% and 11.6%.A distinction is drawn between the initial build-up of nitrogen in circulation and the long term maintenance of a nitrogen level providing maximum recovery of fertilizer N.

Notes: Twin steer calves were used to compare the effects of early weaning indoors with those of rearing on the bucket at pasture. Calves born in the autumn and reared indoors joined their twins at pasture when about 6 months old; those born in the spring were approximately 12 months old when turned out.There was little difference between the performance of indoor- and outdoor- reared calves born in the autumn. Usually, the spring-born calves indoors were about 150 lb heavier than their twins at 12 months of age. This difference normally disappeared by the end of the grazing season and twins became fit for slaughter at the same time. No difference could be found in carcass conformation.

Notes: The water activity of juice available for fermentation, after breakdown of the cell walls during the ensiling of plant material, depends largely on the moisture content of the sample. Water activity increases with moisture content, but probably never becomes so high as seriously to limit lactic-acid fermentation, although high moisture contents have other detrimental effects. With low moisture contents, the limited availability of the juice rather than its lowered water activity is most probably the factor primarily responsible for poor lactic-acid production.

Notes: During the interval from seed set to advanced shedding in a crop of S24 perennial rye-grass, a study was made of: seed drying, the increase in germinating capacity and weight of seed, and the shedding of florets. The seed in early-emerged heads dried more rapidly than that in later heads, and the seed in the upper parts of each spike was drier than in the lower parts. Seeds in early heads attained maximum germination values about 18 days after anthesis. The maximum value was lower in later heads and was not reached until approximately 26 days. Seed in early heads was 67% heavier than that in late heads and the basal florets in each spikelet contained heavier seed than more distal ones. The maximum weight of individual seeds was reached at about the same time in early-emerged and intermediate heads, at about 22 to 26 days after anthesis. Seed in late heads continued to inerease during the whole interval studied. Shedding began before seed reached maximum dry weight and continued at a constant rate. The combination of these processes led to the maximum yield of seed, of 100% germination, being obtainable over a period between 20 and 26 days after anthesis. Criteria are given which would permit this stage to be recognized.

Notes: Seeds of four legumes and four grasses were germinated in the presence of aqueous extracts of the same species, using distilled water as a check. Measurements were taken to determine the effect of the extracts on germination, root growth and shoot growth. Based on the number of significant reactions to the extracts, the species may be classified in the following order of decreasing inhibition: alfalfa, birdsfoot trefoil, Ladino clover, red clover, reed canary grass, brome grass, timothy and orchard grass. Conversely, alfalfa and timothy were the species least affected by the extracts while reed canary grass was the most susceptible. Other species were in an intermediate range. With the exception of alfalfa, extracts of aerial portions of the plants had greater inhibitory effects than root extracts.

Notes: Tools and technique for sampling pit silage to determine dry matter and density are described.

Notes: A survey was made of the flowering responses of 47 annual, biennial and perennial grasses, to measure the extent of any winter requirement for floral induction, and to see how far this could be provided by controlled cold or short-day treatment.The annual species showed little or no inductive requirement, nor did the perennials Arrheuatherum elatius, Ceratochloa unioloides, Phleum pratense and Poa nemoralis. Most perennials possessed a definite inductive requircinent. A few species, such as Lolium perenne, responded to both cold and short-day given to the young seedling, while others, such as Phleum nodosum, Agrostis alba, A. canina, A. stolonifera and A. tenuis, responded to short-day induction but not to cold.Many temperate perennials, however, including Cynosurus cn'status, Dactylis glomerata, Festuca pratensis, F. rubra, Poa pratensis and P. trivialis did not respond to seedling induction and possibly have a juvenile stage before they are able to respond to inductive conditions.The sequence of flowering responses in the temperate perennial grasses is evidently more complex than was previously thought, and the perennial habit can be achieved by many different developmental pathways.

Notes: A small-scale conservation experiment is described in which molasses, zinc bacitracin and dried sugar-cane juice were compared as additives to grass silage. The results indicate that all these additives improved the quality of the silage, but do not suggest any significant decrease in dry-matter loss due to the use of preservatives.