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XXIII. Notices respecting New Books. 



Researches of the Department of Terrestrial Magnetism. Land 

 Magnetic Observations 1905-1910. By L. A. Bauer, Director 

 of the Department. (Quarto; pp. 185.) Washington, 1912. 



r r\HE Department of Terrestrial Magnetism of the Carnegie 

 Institution of AVashington came into existence in April 1904, 

 and has for one of its principal objects the acquisition of the data 

 necessary for a general magnetic survey of the Earth. This volume 

 deals with all the land observations made by the Department up 

 to the end of 1910. It gives a general account with illustrations 

 of the types of: instruments used, describes the methods of taking 

 and reducing observations, and enumerates in tabular form the 

 values obtained for the magnetic elements at 1298 stations scat- 

 tered over the globe. The continents chiefly represented are 

 Africa with 38b' stations, Xorth America with 328, and Asia with 

 308. The observers — including some foreigners employed on 

 special expeditions — numbered 35. Descriptions are given in- 

 tended to fix the exact site of each station, and a number of 

 interesting photographs collected in plates show representative 

 sites in different parts of the world. 



Practical Measurements in Radio-activity. By AV. Makower, M.A., 

 B.Sc, and H. G-eiger, Ph.D. Pp. ix 4-151. Longmans, Green 

 & Co. 1912. Price os. net. 



The well-known researches of both the authors of this book are 

 sufficient to inspire confidence in the reader even before he reads 

 the book itself, and the confidence is not misplaced. The authors 

 have a first-hand acquaintance with the subject and, besides this, 

 one of them at least has a large experience as a teacher. The 

 result is a book which is a complete compendium of the science 

 of radioactivity from the point of view of practical measurements, 

 with enough of the theory thrown in to make the volume self- 

 contaiued. On the physical side perhaps the most important 

 chapter is that on standard measurements, while the final chapter 

 deals with the various methods, both chemical and other, of 

 separating radioactive substances. Three appendices contain 

 tables of radioactive constants, tables of decay of radioactive 

 substances, and notes on radioactive materials and measuring 

 instruments. 



