274 



SCIENCE. 



[N. S. Vol. XVIII. No. 452. 



scarcely necessary for the present Writer to 

 repeat what he has said in commendation of 

 Mr. Gage's skill as a text-book writer, mani- 

 fested in other books reviewed in the columns 

 of Science. He is fully up to the standard 

 set in those volumes. 



The third group of text-books, intended for 

 parallel reading or private study, is exempli- 

 fied by the last three books on our list. This, 

 perhaps, might be expected from the fact that 

 the authors are writing for readers on the 

 other side of the Atlantic, two of them being 

 English and the third a Eussian. There has 

 been a distinctly American evolution of edu- 

 cational methods; and this fact, quite inde- 

 pendently of any author's individual merit, 

 causes few foreign text-books to be now avail- 

 able for text-book purposes in American 

 schools, except for advanced students. 



Lehf eldt's ' Text-Book of Physics ' is writ- 

 ten for students of medicine, and the author 

 has endeavored, therefore, to exclude mathe- 

 matical formulas as much as possible. The 

 mode of arrangement is not to be commended, 

 there being many long paragraphs and but 

 little to aid the reader in singling out salient 

 points. It is impossible to avoid formulas 

 entirely, and these are incorporated quite fre- 

 quently in the midst of the paragraphs, in- 

 stead of being put separately and equationally 

 so that mutual relations may be readily per- 

 ceived. The book contains no problems. 

 Chapter VI., entitled ' Chemistry,' is made up 

 wholly of paragraphs in fine print on such 

 subjects as the law of mass action, the phase 

 rule, thermo-chemistry, and the relation of 

 heat to chemical equilibrium. A single para- 

 graph of this fine print, considerably more 

 than a page in length, consists of seventeen 

 sentences. The book was written with a view 

 to attracting attention to the intimate de- 

 pendence of physiology on physical principles, 

 "and is made up of the author's lectures to 

 students preparing for the intermediate ex- 

 amination at London University. 



Edser's ' Light for Students ' is written by 

 one who is far better versed in the art of 

 book-making. The paragraphing is good. 

 The illustrations, chiefly diagrams with white 

 lines on a black ground, are clear and well 



selected. Mathematical formulas are used 

 wherever necessary, and the deduction of 

 them is usually in good shape, no knowledge 

 of calculus being assumed. In discussing the 

 wave theory the author recognizes the recti- 

 linear propagation of light, not as a ' fiction ' 

 but as a resultant of wave motion, and light 

 rays are assumed equally with wave fronts 

 whenever suggested by convenience. Among 

 the illustrations are several selections from 

 Professor Wood's excellent photographs of air 

 waves taken by the ' Schlieren-Methode.' 

 Modern advances are noticed, including the 

 production of stationary light waves by 

 Wiener and Lippmann, the interferometer 

 work of Miehelson, and his echelon grating. 

 The light phenomena accompanying electric 

 discharges in high vacua come in for atten- 

 tion. X-rays being regarded as probably those 

 of ultra-violet light of extremely short wave- 

 length. The radiation from salts of 

 uranium, polonium, actinium and radium is 

 mentioned, but as the date of the preface is 

 September, 1902, this subject is noticed more 

 briefly than it would be to-day. The book 

 is, on the whole, much to be commended. 



The first volume of Chwolson's ' Physics ' 

 was published in 1897, at St. Petersburg, in 

 the Russian language. A second edition ap- 

 peared in 1900 and was brought to the atten- 

 tion of Professor Wiedemann at Erlangen. 

 Appreciating its excellence, he took steps to 

 secure its translation into German. This 

 task was undertaken by Dr. Pflaum in Riga 

 and the risk of publication assumed by Vieweg 

 in Braunschweig. 



Of late years two notable books on chem- 

 istry have come from Russians, the one by 

 Mendelejeif, the other by Menschutkin; but 

 neither could exert any important influence 

 on the scientific world until freed from the 

 shackles of an unspeakably difficult language. 

 Chwolson's book is now in process of sim- 

 ilar deliverance, and it has already received 

 marked attention in Germany. The first 

 volume, of nearly 800 pages in German, re- 

 lates to the mechanics of gases, liquids and 

 solids. The second, on acoustics and radiant 

 energy, was to appear in Russian in 1898. 

 The third relates to heat, and the fourth to 



