Geology and Natural History. 191 



12. Die Strahlen der positiven Elektrizitat • von E. Gehrcke. 

 Pp. xi -f- 124. Leipzig, 1909. (S. Hirzel.) — This is an excellent 

 and timely account of a class of radiations which have oflate years 

 come to be of great importance in physics. The rays which con- 

 sist of positively charged particles include the canal rays dis- 

 covered many years ago by Goldstein, certain other rays which 

 are observed in ordinary vacuum tubes, the a-rays from radio- 

 active substances and the "anode rays" (recently discovered by 

 Gehrcke and Reich en heim), which are given out by anodes con- 

 sisting of the salts of various metals. The properties of all these 

 rays and their accompanying phenomena are described in detail, 

 and the book forms a very useful collection of data upon an 

 important subject. h. a. b. 



II. Geology and Natural History. 



1. United States Geological Survey, Thirtieth Annual Report, 

 1908-1909, of the Director, George O. Smith. Pp. 128, with 

 two plates. — This report contains a statement of the work done by 

 the various divisions of the Survey during the fiscal year ending 

 June 30, 1909. Besides the progress in geologic investigations 

 and topographic mapping, for which the Survey was initially 

 organized, the special lines of work which Congress has delegated 

 to it are worthy of note. The classification of public lands has 

 been carried forward with great activity, resulting in a proper 

 valuation of land according to the use for which it is most valua- 

 able. As a consequence the government is deriving a revenue 

 from the sale or lease of said lands many times greater than the 

 cost of the surveys. Fraudulent entries are made more difficult 

 and monopolistic control is prevented, but immediate utilization 

 is fostered ; the present system resulting in the greatest good to 

 the nation at large. 



The division of mine accidents has been organized within the 

 year, studies have been carried on in Europe and in this country 

 and already large results begin to show toward the prevention of 

 the destruction of both human life and mineral resources. 



The technologic branch by its investigations of materials used 

 in government contracts has, during the year, guarded the 

 expenditure of tens of millions of dollars and saved millons to 

 the government. 



Because these additions to the work of the Survey are so imme- 

 diately important and popularly recognized as of great value, 

 conscious effort should be maintained to prevent their encroach- 

 ment upon the equally valuable purely scientific work upon 

 which such developments ultimately rest. That Congress does 

 not fully appreciate this broader view is shown by the fact that 

 the Survey was only granted $100,000 for stream measurements, 

 whereas $250,000 was appropriated for testing fuels. For topo- 



