348 



SCIENCE 



[N. S. Vol. LIV. No. 1398 



related to the atomic numbers in a definite 

 manner is brought out by the curve which 

 Harkins^^ has worked out and in a more 

 striking fashion the curve given by Dush- 

 man^s relating the logarithms of the suscepti- 

 bilities of the elements to the atomic numbers. 

 The curves showing these relations indicate a 

 vei-y definite tie between them and yet there 

 seems to be no other properties associated with 

 atomic numbers which are definitely related 

 to the susceptibilities of the elements. May 

 not this fact also emphasize the importance 

 of placing some of the magnetic properties 

 of the elements in the nuclei? 



To come back to the field of magnetostric- 

 tion it would appear from its teaching that 

 in addition to electronic orbits, to explain 

 magnetic susceptibility, there must he given 

 io the positive nucleus of the atom a proper- 

 ftp of induction just as Ewing had in his ele- 

 ■mentary magnets, and, for ferromagnetic sul- 

 ^tances at least, those nuclei ought to have 

 ■different dimensions in different directions, 

 •capable of heing rotated hy means of an ex- 

 ternal field. 



Helmholtz once said, 

 ■ The disgrace of the nineteenth century is our 

 ignorance concerning magnetism. 

 What shall we say of the twentieth century? 

 S. E. Williams 



Oberlin College, 



■ Oberlin, Ohio 



FUNDAMENTAL PRINCIPLES ESTAB- 

 LISHED BY RECENT SOIL IN- 

 VESTIGATIONS 



introduction 



The following is a brief review of the 

 fundamental principles established by modern 

 methods of soil investigation in the Bureau 

 of Soils in the past twenty or thirty years: 



TEXTHRF. OF SOU. 



The first step taken established the fact of 

 the general influence of the texture of the 



32 Harkins and Hall, Journ. Amer. Chem. Sac, 

 38, 210, 1916. 



33 Dushman, I. c. 



soil and its water-holding capacity on the 

 distribution of the great classes of crops; that 

 is, the general relation between the sand, 

 fine sand, silt and clay soils and the general 

 distribution of areas devoted to the produc- 

 tion of truck crops, corn, wheat, hay and other 

 heavy farm crops. This together with field 

 studies of origin, mode of formation, and ob- 

 servable physical differences led to the map- 

 ping of soils, or the soil survey, which has 

 been extended over a considerable part of the 

 United States. 



With the wide field experience it became 

 evident that differences existed between dif- 

 ferent soil types or in the same soil type 

 that were not to be explained by differences 

 in texture or in water-holding capacity, but 

 that yields vary with the practise of the 

 farmer or from other causes, as was fully 

 known and commented upon by the early 

 Roman writers, that would need to be ex- 

 plained before the practise of agriculture, the 

 application of fertilizers, and the handling of 

 soils could be put upon a truly scientific 

 basis. 



ORGANIC CHEMISTRY OF SOILS 



The study of some notably infertile soils 

 and of very productive soils of the same typ>e 

 which had been held under what we call 

 " better systems of farming " revealed the 

 presence of certain toxic organic compounds 

 in the one which were not present in the 

 other. This led to a study of the organic 

 chemistry of the soils. Finally we succeeded 

 in separating from soils some 35 definite 

 organic compounds, some of which were bene- 

 ficial to certain crops and some of which were 

 toxic to certain crops and nontoxic to others. 

 It was also found that soils under a certain 

 condition of aeration would yield certain 

 organic products and under other conditions 

 of aeration other organic products. It was 

 found that the compounds separated from the 

 soil were of the same nature as the comjwunds 

 in the digestive system and in the blood of 

 man and animal and it was finally realized 

 that the soil has a digestive system as it were 

 and breaks down organic materials such as 

 the proteins, carbohydrates, and fats much 



