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XVI. Notices respecting New Books. 



Physics, an elementary text-book for University Classes. Third 

 Edition. By C. G. Knott, D.Sc., E.B.S.E. Pp. vi-f-292 + 

 370 (Two parts). London and Edinburgh: W. & R. 

 Chambers. 1913. Price 7s. 6d. 



r pHIS text-book is destined for the use of junior University 

 -*- Students, and especially medical ones, in their first year of 

 study. The first edition was published before the discovery of the 

 phenomena of radioactivity. The present, third, edition is therefore 

 enlarged, in its Second Part, dedicated to " Matter, Ether and 

 Energy," by a new chapter (pp. 336-350) on " The Electron 

 Theory and Radio-Activity," and, in connexion with this, by short 

 indications concerning the recent advance in various lines of 

 physical research. The new chapter contains a short description 

 of the kathode, anode, and Rontgen rays, of the discoveries made 

 by Becquerel and the Curies, and of the a, /3, and y rays, followed 

 by short sections on " The Emanations and Active Deposits," the 

 "Energy of the Radiations," and the "Distribution of Radio- 

 Active Bodies." The subject of that chapter gives the author an 

 opportunity of intercalating some of the concepts of the electron 

 theory. 



Photoelectricity : The Liberation of Electrons by Light. By H. 

 Stanley Allen, D.Sc. Pp. vii-j-221, Longmans, Green 

 & Co. 7s. Qd. net. 



This book, which is one of the Monographs of Science which 

 Messrs. Longmans, Green & Co. are now publishing, illustrates very 

 well the remarkable growth in electronic science during the last two 

 decades. Eor although it extends to over two hundred pages it 

 deals with only one small portion of that science, and yet perforce 

 — owing to the enormous mass of detail to be dealt with — is com- 

 pelled to treat it in a very summary fashion. Use made of the 

 volume since the reviewer received it convinces him that it gives a 

 very thorough account of the subject, and where room has been 

 found for criticism or comment Dr. Allen has been able to supply 

 it with a sound judgment based upon a thorough knowledge of 

 the facts. The subject is still growing fast and existing theories 

 cannot be regarded as much more than tentative guesses after the 

 truth. It is this fact which must have made the book exceedingly 

 difficult to write. It would be futile to claim that the volume 

 left one without any sense of confusion; but we think that 

 Dr. Allen can hardly be blamed for this ; it is simply the result 

 of his being obliged to compress so much growing material into 

 such a small space. 



It is the first detailed account of the subject in English, and 

 should be in the hands of every student. JS T ot the least inter- 

 esting chapter is the last, on the photographic image. 



