Geology. 83 



following words: — "A so called knowledge of elementary 

 science which does not relate to some actual physical condition 

 or thing is superlatively contemptible." d. a. k. 



11. Direct and Alternating Current Testing ; by Frederick 

 Bedell ; assisted by Clarence A. Pierce. Pp. x, 265. New 

 York, 1909 (D. Van Nostrand Co.). — To call this book a labora- 

 tory manual of tests on direct and alternating currents, would 

 not be doing it justice. The consideration given to the under- 

 lying principles of the experiments, as well as to the significance 

 of the results, places it both in the category of reference and of 

 text books. It is not offered as an exhaustive treatment of the 

 subject but is sufficiently comprehensive to give the student a 

 good working knowledge. It presupposes only the usual college 

 courses in physical and electrical measurements. The subjects of 

 the seven chapters are :- D.C. generators; D.C. motors; synchron- 

 ous alternators ; single phase currents ; transformers ; polyphase 

 currents ; phase changers, potential regulators, etc. Other chap- 

 ters on A.C. motors and converters are promised in a later 

 edition. d. a. k. 



12. Elements of Physics; by Henry Crew. Revised by 

 Franklin T. Jones. Pp. xiv, 435. New York 1909 (The 

 Macmillan Co.). — This high school text is a revision of Crew's 

 original Elements of Physics and embodies much of his more 

 recent General Physics. The insides of the covers contain the 

 English and Metric systems of weights and measures,' with tables 

 of their equivalents. In the appendix are given 370 questions 

 reproduced from examination papers of various high schools 

 throughout the country. Definitions and leading statements are 

 emphasised by bold-faced type, and numerous problems are 

 embodied in the text. It is to be hoped that in the next edition 

 the authors may eliminate such slips as "knots per hr.," "attraction 

 of gravity, g," "in physics rate always means 'divided by time' ", 

 and revise the somewhat misleading discussion of harmonic 

 motion. d. a. k. 



II. GrEOLOGY 



1. Radio-activity and Geology. An account of the influence 

 of radio-active energy on terrestrial history / by J. Joly. Pp. 

 287. London, 1909 (Archibald Constable & Co., Ltd.).— This 

 book is an outgrowth of the author's presidential address to Sec- 

 tion C of the British Association and brings into one volume the 

 present information regarding radio-activity in its bearings on 

 geology. Geologists will consequently find it a most welcome 

 volume since but few have the time or opportunity to follow in 

 the physical journals the rapidly accumulating results of recent 

 investigations. 



The first larger subject treated is that of radium in the earth's 

 surface materials. Many measurements have now been made on 



