SCIENCE 



Friday, August 13, 1920 



CONTENTS 

 Agricultural Geology: Peofessoe John E. 

 Smith 139 



The Nomenclature of Families and Subfam- 

 ilies in Zoology: De. Haeey C. Obeeholser. 142 



Further Besults of Analysis of Light Deflec- 

 tions observed during the Solar Eclipse of 

 May S9, 1919 : De. Louis A. Bauee 147 



Scientific Events: — 



Chemical Research in France and England; 

 Medical Education in the United States; 

 WorTc of the Bureau of Mines; The Beor- 

 ganization of the Nela Research Laborator- 

 ies; The Lister Memorial 148 



Scientific Notes and News 151 



University and Educational News 153 



Discussion and Correspondence: — 



Transverse Vibrations of Bods: Peofessoe 

 Aethue Goedon Webstee. The Explora- 

 tion of Venezuela: E. B. Williamson. 

 Mathematisolie Zeitschrift: Peofessoe 6. 

 A. Miller 154 



Scientific Boohs: — 



Gold's Aids to Forecasting : A. M 155 



Special Articles: — 



Linked Genes in BalMts: Peofessoe W. E. 

 , Castle. The Fat-soluble A Vitamine and 



Xerophthalmia: De. A. D. Emmet 156 



The American Cliemical Society: De. Chaelbs 

 L. Parsons 158 



MSS. intended for publication and books, etc., intended for 

 review should be sent to Tlie Editor of Science, Garrison-on- 

 Hudaon, N. Y. 



AGRICULTURAL GEOLOGY 



During reconstruction, as the present period 

 is frequently termed, many new applications 

 of the principles of pure science to special 

 fields of endeavor are being made. The prin- 

 ciples of geology thus applied during recent 

 years have given rise to economic geology, 

 mining geology, engineering geology, oil geol- 

 ogy and perhaps to that branch of the subject 

 indicated by the above title for it is not en- 

 tirely new. The application of the principles 

 of the science to the solution of the geological 

 problems that are met in agricultural enter- 

 prises and pursuits, in brief, the relation of 

 geology to rural welfare may appropriately be 

 considered as agricultural geology. 



Such a problem is that of securing an abun- 

 dant supply of pure water. In regions of 

 copious rainfall it is essential, in those of aver- 

 age to minimum rainfall it is absolutely neces- 

 sary to consider the properties and the struc- 

 ture of the substrata in their relation to water 

 in order to obtain such a supply. Pursuant to 

 the requirement of this necessity, the United 

 States Geological Survey maintains a branch 

 of service whose work is concerned with the 

 ■water resources of the entire country. The 

 purity of su'bsurface water depends dhiefly on 

 the filtering ^power of the yielding rocks. One 

 of the best natural filters consists of residual 

 material of considerable depth. Some rocks 

 below this mantle are sufficiently pervious to 

 bold, transmit, filter and consequently to yield 

 pure water. Certain others are impervious. 

 Another condition is found where the rocks 

 contain joints or cracks along which water 

 moves freely without filtration, conveying to 

 wells or springs contamination from distant 

 sources. This condition is a strong possibility 

 in limestone regions. Artesian water which, 

 jn some localities, flows from wells may be 

 found where the properties and structure of 



