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  • 1
    Electronic Resource
    Electronic Resource
    Kepler's Laws of Planetary Motion: 1609–1666 (1964)
    Cambridge : Cambridge University Press
    The @British journal for the history of science 2 (1964), S. 1-24 
    Details
    ISSN: 0007-0874
    Source: Cambridge Journals Digital Archives
    Topics: History , Natural Sciences in General
    Notes: SynopsisHistorians of seventeenth-century science have frequently asserted that Kepler's laws of planetary motion were largely ignored between the time of their first publication (1609, 1619) and the publication of Newton's Principia (1687). In fact, however, they were more widely known and accepted than has been generally recognized.Kepler's ideas were, indeed, rather slow in establishing themselves, and until about 1630 there are few references to them in the literature of the time. But from then onwards, interest in them increased fairly rapidly. In particular, the principle of elliptical orbits had been accepted by most of the leading astronomers in France before 1645 and in England by about 1655. It also received quite strong support in Holland.The second law had a more chequered history. It was enunciated in its exact form by a few writers and was used in practice by some others without being explicitly formulated, but the majority, especially after 1645, preferred one or another of several variant forms which were easier to use but only approximately correct. The third law attracted less interest than the others, chiefly perhaps because it had no satisfactory theoretical basis, but it was correctly stated by at least six writers during the period under review.Between about 1630 and 1650 Kepler's Epitome Astronomiae Copernicanae (in which all three laws were clearly formulated) was probably the most widely read work on theoretical astronomy in northern and western Europe, while his Rudolphine Tables, which were based upon the first two laws, were regarded by the majority of astronomers as the most accurate planetary tables available.Kepler's work certainly did not receive all the recognition it deserved, but the extent to which it was neglected has been much exaggerated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1017/S0007087400001813
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    Paper (German National Licenses)
    Fulltext
  • 2
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    The efficiency of pneumatic tyred tractors under farm conditions (1942)
    Cambridge University Press
    Details
    Publication Date: 1942-01-01
    Description: 1. Increasing the ballast on pneumatic tyres, up to a certain weight, improves the tractor performance as judged by its speed, fuel consumption and wheel slip. Further increases beyond this point continued to decrease the wheel slip without having any marked effect on its speed or fuel consumption. No certain evidence was obtained that too heavy a ballast decreased the tractor's efficiency.2. The tyre load affects the maximum pull the tractor can exert while working reasonably efficiently, but this pull does not depend markedly on the speed of work. Wheel weights of about 12–13 cwt. seem to be the minimum required for optimum performance of the 36 or 28 in. tyres at pulls of 1800 lb. under fairly good ground conditions, and possibly a greater weight may be required by the 24 in. tyre.3. If the tractor is ploughing it is usually running tilted, and this tilt transfers sufficient weight on to the furrow wheel for it to work efficiently under most conditions. Additional ballast is, however, often necessary for the lighter land-side wheel.4. Tyre performance is much less dependent on inflation pressure than on ballast. Pressures below 10 lb./sq. in. were only of use in wet conditions when small amounts of additional ballast were not available. Pressures above 12 lb./sq. in. may allow excessive slip to take place and probably only need be used on the furrow wheel of a well-loaded tractor ploughing.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 3
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    The determination of the volume and air space of soil clods (1944)
    Cambridge University Press
    Details
    Publication Date: 1944-07-01
    Description: A method is described for determining the field volume and the air space of a clod of any shape by filling its pores with a hydrocarbon oil, such as paraffin or tetralin, and determining its weight in the oil and in air before and after impregnation. The method appears to work well for clods of any moisture content.This method is shown to give values of these volumes entirely comparable with those given by the other accurate methods described in the literature. Its accuracy for clods of Rothamsted soil, weighing between 20 and 500 g., was probably at least 1 part per thousand, i.e. 0-1%.The method has been applied to the determination of the available water held by a soil and has been used to illustrate the effect of long-continued applications of farmyard manure to a soil in increasing the amount of available water it can hold.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 4
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    The subdivision of the clay fraction in mechanical analysis (1943)
    Cambridge University Press
    Details
    Publication Date: 1943-07-01
    Description: An examination has been made of the possibility of extending the routine mechanical analysis of soils down to finer particles than the conventional clay. The main conclusions reached are:(1) Sampling depths of only 2 cm., using standard mechanical analysis apparatus, appear to introduce no new sources of error.(2) If a constant temperature room is available, sampling times of 7 days seem to be allowable.(3) Using special pipettes and settling vessels, sampling depths of only 2½ mm. seem to be allowable.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 5
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    The magnetohydrodynamic squeeze film (1964)
    Cambridge University Press
    Details
    Publication Date: 1964-07-01
    Description: Magnetohydrodynamic squeeze films are investigated theoretically and experimentally. The theory of magnetohydrodynamic lubrication as applied to squeeze films is extended to include fluid-inertia effects and buoyant forces. Excellent agreement is obtained between theory and experiment. © 1964, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 6
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    Texas Bio-Nuclear Radiocarbon Measurements I (1963)
    Cambridge University Press
    Details
    Publication Date: 1963-01-01
    Description: Texas Bio-Nuclear is a proprietary establishment engaged in offering C14 dating by the liquid-scintillation method as a service to those institutions and individuals who have a need for such a service. The Laboratory began actual dating operations in December 1961. The first few months were devoted to processing check samples in order to establish the reliability of the system. The dates listed below are not inclusive of all our dating, since the dates we furnish our clients are their property and the publishing of this information is their decision.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 7
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    Birth weights of reciprocally cross-bred calves (1962)
    Cambridge University Press
    Details
    Publication Date: 1962-06-01
    Description: This study is based on 1015 live single calves brod by artificial insemination in a herd of Ayrshire, Friesian, Jersey and two-breed and three-breed cross cattle derived from them. Birth weights, subjected to a least squares analysis, show little effect of year or season of calving. Males were 6·0 lb. heavier than females; second and later parity calves were 6·6 lb. heavier than first parity calves.Over the range of breeds and crosses studied, heredity was the principal determinant of mean birth weight. No evidence of heterosis was found— means for crossbred calves, however, differed in reciprocal crosses. They deviated from the mean of the parents in the direction of the maternal weight at birth. If 0 is the mean birth weight of the dam's breed or cross and 0 of the sire's breed, the mean weight of offspring is closely estimated byThis expression may not apply to the crossing of breeds differing much more in weight than the Jersey and Friesian breeds. In such crosses it is likely that small dams depress foetal growth more than large dams promote it. The maternal influence on birth weight in cattle as expressed above is in both qualitative and quantitative agreement with the maternal influence as derived from egg transfer studies in sheep.It is a pleasure to record the authors' heavy obligations to many friends for help during the course of this long experiment. The Milk Marketing Board, in the persons of Dr J. Edwards, C.B.E., Mr T. O'Sullivan, and their colleagues at the A.I. centres made the breeding programme possible. Much time has been saved and much statistical computation cut short by the help afforded us at the Rothamsted Statistical Department by Dr F. Yates and his staff, particularly Mr J. H. A. Dunwoody. Responsibility for the animals on the farms fell at first upon Mr W. S. Biggar, and from 1950 upon Mr J. S. Tavernor. They were aided by many of whom mention must be made of Mr H. L. Williams, Mr R. Pringle and Mr R. Simpson. In the preparation of this paper the authors have been much influenced by the work and criticism of their colleagues.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 8
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    Studies in soil cultivation: XI. The effect of inter-tillage on the sugar-beet crop (1942)
    Cambridge University Press
    Details
    Publication Date: 1942-07-01
    Description: Experiments on the effect of inter-row cultivation of sugar beet, carried out in the three years 1939–41 on a sandy loam, led to the following results:1. If the soil nutrients are in short supply hoeing or hand-weeding increases the yield of the beet, provided these operations are carried out before or shortly after singling.2. Hoeing is more effective than hand-weeding, but it cannot yet be said with certainty whether this is due entirely to more efficient weed destruction, or whether there is some additional effect, such as mulching.3. If adequate quantities of soil nutrients are present, inter-row cultivation has little effect on yield, and the crop can tolerate a considerable weed infestation without any effect on yield.The results for sugar beet on the heavy clay-with-flints soil at Rothamsted show:1. Additional hoeings after singling, above a modest minimum, have either no effect on yield or else depress it.2. On the one occasion when pre-singling cultivations were given, the yield was increased.3. In contrast with the Woburn results the effect of cultivation does not vary with, the level of manuring.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 9
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    The determination of the size distribution of soil clods and crumbs (1940)
    Cambridge University Press
    Details
    Publication Date: 1940-04-01
    Description: 1. It is possible to determine the size distribution of clods in the field by simple sieving of the soil without any pre-treatment provided the soil is not too wet. There is a personal factor involved in the sieving, but with care and training this will not affect comparisons of results obtained by that person. If the soil is too wet the individual clods smaller than 3 mm. stick together on the 3 mm. sieve. This sticking together is first apparent on the 3 mm. sieve but may become appreciable on the ¼ in. (6 mm.) sieve. No certain way was found for overcoming this difficulty.2. There appears to be no best method for determining the size distribution of the soil crumbs, i.e. of the water-stable aggregates in the soil. The method and the technique must be chosen so as to give the maximum amount of useful information. If an appreciable proportion of the crumbs are larger than ½ mm., a water-sieving method is practically essential.3. The method of wetting to be used can only be chosen from a consideration of what information is wanted. If possible it would be desirable for general purposes to use a very slow or a vacuum wetting technique and a very rapid wetting technique such as wetting the soil by immersion in water.4. The decision whether air-dry or field-moist soil should be used depends entirely on the information needed. For general purposes the use of air-dry soil is recommended.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 10
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    Studies in soil cultivation: X. The results of a six-year cultivation experiment (1941)
    Cambridge University Press
    Details
    Publication Date: 1941-07-01
    Description: 1. The results of a six-year cultivation rotation experiment are given. The rotation used was wheat-mangolds-barley and the seed-beds for these were prepared either by ploughing, using a rotary cultivator or a tractor-drawn grubber.2. The yields of these crops were barely influenced by the depth of ploughing, a 4 in. depth giving throughout the six years just about the same yield as an 8 in. depth. The mangold crop was possibly a little larger on the deeper ploughed plots.3. The mean yields of the seed-beds prepared with the tractor drawn grubber or cultivator followed by harrows etc. were lower than the ploughed seed-beds for all the crops, and this was particularly so on those seed-beds prepared by only one grubbing down to 4 in. depth.4. The mean yields on the seed-beds prepared by the rototiller were lower than on the ploughed seed-beds for wheat and mangolds. If the seed-bed was prepared by rototillage to a depth of 8 in. by going over the land twice, the yield of barley was the same as on the ploughed seed-beds, but was definitely less on the seed-bed rototilled only once to 4 in.5. Seed-beds prepared by the rototiller or grubber have only a small residual effect on the crop yields in the following year.6. It is concluded that the primary function of ploughing is weed control, and that it is only advisable to omit ploughing either if the land is already fairly clean or if the crop will be hoed very early on in its development.7. For wheat and mangolds differences in weed infestation of the seed-bed were probably of greater importance than differences in tilth in so far as the crop yield was concerned. The reverse may have been true for barley.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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