474 



NATURE 



[July io, 1913 



have no such theory of the origin of objects which 

 they supposed to be divinely produced. These 

 facts being admitted, a different explanation sug- 

 gests itself as being more probable. Such things 

 usually come to light after torrential rains, and 

 are thus naturally attributed to the thunder which 

 accompanies the storm; and thus, besides flint 

 axes, things like belemnites, fossil echini, and 

 other quaintly shaped stones come to be revered 

 like lithic artefacts. 



It is also very doubtful if Mjolnir, the hammer 

 of Thor, or the double-axe of Crete come within 

 this category. The former was not a stone, but a 

 forged metal axe, and the sanctity of the latter 

 was possibly due to its use as a sacrificial imple- 

 ment. Poseidon's trident, again, was more prob- 

 ably the fish-spear which is the natural weapon of 

 a sea-god. 



In short, thunderstones, sacred fossils, sacred 

 axes, and tridents may have their origin in general 

 animistic conceptions, and their cult need not 

 necessarily have arisen in any single centre or from 

 any one train of thought. However this may be, 

 the facts which the author has collected form a 

 useful contribution to the study of primitive beliefs. 



PURE AND APPLIED CHEMISTRY. 



(1) Problems in Physical Chemistry with Practical 

 Applications. By Dr. E. B. R. Prideaux. 

 Pp. xii + 311. (London: Constable and Co., 

 Ltd., 1912.) Price ys. 6d. net. 



(2) An Introduction to the Physics and Chemistry 

 of Colloids. By Emil Hatschek. Pp. ix + 94. 

 (London: J. and A. Churchill, 1913.) Price 

 25. 6d. net. 



(3) Exercises in Gas Analysis. By Dr. Hartwig 

 Franzen. Translated from the first German 

 edition (with corrections and additions by the 

 Author) by Dr. Thomas Callan. Pp. vii+120. 

 (London : Blackie and Son, Ltd., 1913.) Price 

 2s. 6(7. net. 



(4) Theorie und Praxis der Grossgasindustrie. 

 By Rudolf Mewes. Band 1. Halfte 1. Pp. 

 xx +403. (Leipzig: H. A. Ludwig Degener; 

 London : Williams and Norgate, n.d.) Price 

 185. net. 



(5) Lchrhuch der Therinochemie und Thcrmo- 

 dynamik. By Prof. Otto Sackur. Pp. viii + 

 340. (Berlin : Julius Springer, 1912.) Price 

 12 marks. 



(6) A Foundation Course in Chemistry. For 

 Students of Agriculture and Technology. Bv 

 J. W. Dodgson and J. Alan Murray. Pp. 

 x + 244. (London: Longmans, Green and Co., 

 1913.) Price 3s. 6d. net. 



NO. 2280, VOL. 91] 



(7) Qualitative Determination of Organic Com- 

 pounds. By J. W. Shepherd. Pp. xvi + 348. 

 (London: W. B. Clive, 1913.) Price 6s. 6d. 

 (1) T^vR. PRIDEAUX has compiled a book of 

 1 J problems to serve as exercises for 

 students in physical chemistry. The students who 

 have worked through these will not be able to 

 complain that they have not been exercised suffici- 

 ently, as the examples selected are very numerous 

 and by no means all easy. They are, however, 

 selected directly from the original literature, and 

 so require the student to give real solutions to 

 real problems, instead of the sham answers to 

 fictitious questions which so frequently disfigure 

 books of chemical calculations. The form in 

 which this excellent material has been published 

 is much less satisfactory. The table of contents 

 suggests that the volume is composed of eight 

 chapters, but these do not appear in the text. 

 The reader is informed on each of the 300 pages 

 that the book he is studying is called " Problems 

 in Physical Chemistry," but no hint is given as 

 to the topic that is dealt with on the pages at 

 which the book is opened. The eight chapters 

 run on continuously, and almost the only way to 

 discover where one chapter ends and another begins 

 is to turn back to the table of contents, for the 

 chapters are not even allowed the luxury of begin- 

 ning at the head of a fresh page. As no index 

 has been supplied, the contents of the book are far 

 less accessible than they need be to a reader who 

 does not wish to work right through the book from 

 beginning to end. 



(2) A somewhat similar complaint may be made 

 in reference to the reprint of Mr. Hatschek 's 

 articles on colloids. These are divided into ten 

 chapters, but the chapter-divisions do not corre- 

 spond in every case with the natural divisions of 

 the subject, and subject-headings are not given, 

 so that the classification of the material is not 

 immediately obvious. This defect is, however, 

 very largely remedied by the provision of a very 

 detailed table of contents and two indexes. The 

 book has the great merit of presenting in a simple 

 and readable form all the leading points of a 

 difficult and little-known subject. It may be 

 commended without hesitation to the many 

 readers who at the present day are being com- 

 pelled by the pressure of technical or scientific 

 problems to acquire some knowledge of "colloid 

 chemistry." 



(3) The English translation of Dr. Franzen's 

 "Gas Analysis" forms a very useful introduction 

 to the subject. Directions are given for carrying 

 out forty-two exercises. Thirty-three of these 

 have to do with the analysis of gases. The 

 remainder, which are collected under the heading 



