Chemistry and Physics. 77 



tial expressions for the absorption with increasing thickness of 

 lead. Y. Taomikoskt has used greater thicknesses of lead than 

 Rutherford, McClelland, Wigger and Eve. He finds that the 

 radiation after passing through a noticeable thickness of lead 

 does not diminish exponentially with increasing thickness of 

 lead. — Physik. Zeitschrift, June 1, 1909, pp. 372-374. j. t. 



9. Use of Zinc Sulphate in the Braun Tube. — The Braun 

 tube is of great use in the study of alternating currents and an 

 increase in the spot of light produced by the moving beam of 

 cathode rays on the fluorescent screen is very desirable from the 

 photographic point of view. F. Giesel and J. Zenneck describe 

 the use of zinc sulphide, and show by photographs the advan- 

 tages of its employment. — Physik. Zeitschrift, June 1, 1909, pp. 

 377-379. j. t. 



10. Die Luftelektrizitat. Methoden und Mesidtate der neu- 

 eren Forschung ; von Dr. Albert Gockel. Pp. vi, 206. 

 Leipzig, 1908 (S. Hirzel). — The problem of atmospheric electricity 

 entered a new phase with the discovery of the ionization of gases 

 by Rontgen- and Becquerel-rays and with Wilson's observation 

 that gaseous ions may act as nuclei for the condensation of 

 water-drops. A great amount of work has been done in the last 

 ten or twelve years, especially by Elster and Geitel and their fol- 

 lowers, which will, doubtless, prove to be of great importance to 

 scientific meteorology. Dr. Gockel has done much work of this 

 kind, and in the present volume he gives a most useful resume 

 of the methods and results of the modern investigations of this 

 complex and difficult subject. h. a. b. 



11. La Materia Madiante e i Raggi Magnetici ; by Augusto 

 Righi. Pp. vi, 308. Bologna, 1909 (Nicola Zanichella). — This 

 volume (No. 12 of the series " Attualita Scientifiche ") begins 

 with brief account of cathode, anode, canal and Becquerel rays. 

 The greater part of the book is devoted to the so-called "Mag- 

 netic rays " to which attention has recently been directed, par- 

 ticularly by Villard. Professor Righi proposes the hypothesis 

 that these rays are streams of neutral pairs consisting of a positive 

 ion and a negative electron, rotating about each other. He has 

 made many ingenious experiments which are here described, and 

 which appear on the whole to lend support to his hypothesis. 

 There is a mathematical appendix in which the theory of the 

 motion of such systems is discussed. h. a. b. 



12. A Text-book of Sound ; by Edwin H. Barton. Pp. xvi, 

 687. London, 1908 (Macmillan <fc Co.). — The author has assumed 

 on the part of the student no previous knowledge of sound and, 

 in mathematics, only a knowledge of the elements of the calcu- 

 lus. Nevertheless a student who reads this book will have an 

 extensive and satisfactory knowledge of all the essentials of the 

 subject. The dynamics of vibrating bodies and of wave motion 

 are neither shirked nor neglected, although (very properly) the 

 more intricate and complicated special cases are omitted. The 

 experimental side of the subject is well and fully treated and in 



