5 i8 SCIENCE PROGRESS 



theory of Spiralical or Retrograding progress designed to overcome the difficulty 

 in the theory of re-incarnation that the transmigration of the soul to lower animals 

 seems wasteful of the economy of nature. It is suggested that, originally existing 

 in the non-animal kingdom, the soul progresses through the scale of evolution in 

 a path which can be represented by drawing a solenoid on paper whose successive 

 coils are almost completely circular, lines at right angles to the axis marking 

 the boundaries of animal, human, and spirit worlds. The presentation of the 

 thesis is ingenious, and the writer is unquestionably better able to judge of its 

 suitability for the Eastern mind than the reviewer, to whom the fact that the 

 resultant motion of the earth through space is along a path of the same type hardly 

 appeals as contributory evidence of any value ! The author's final conclusion is, 

 at least, very much to the point ; he exhorts that the Indians should be given their 

 rightful due, "for remember, the Englishmen of this life may be the Indians of the 

 next incarnation " ! 



D. O. W. 



Dynamics : Part I. By R. C. Fawdry, M.A., B.Sc. [Pp. viii + 178 + x Answers, 

 with 94 figures in the text.] (London: G. Bell & Sons, Ltd., 1916. Price 35.) 



This introduction to the study of Dynamics is a very refreshing contribution to a 

 rather overburdened market. 



The term "practical mathematics" — quite safe, perhaps, when used by 

 Prof. Perry — has become truly nauseating as interpreted by many science and 

 technical teachers. No longer is twice two to be four, but, two bricks, increased 

 two-fold, become four bricks. 



Mr. Fawdry has steered a happy mean course between the dry and un- 

 interesting and the ultra-practical by keeping to thoroughly scientific methods 

 in the text and using practical examples and references as illustrations. The 

 interest of the student, thus stimulated, is maintained by historical notes — a truly 

 excellent idea. 



Further, as a text-book it is all a text-book should be, inasmuch as it leaves 

 plenty of scope for the teacher, presenting only the essential points for the student. 



In very strongly recommending this little volume, we have no doubt that 

 teachers will help to remove those small blemishes that are bound to be found in 

 all new works and editions. Thus, in Example 8, page 31, " How far does it fall 

 in 6 sees, and in 12 sees. ?" should read, " in the first 6 sec. and in the first 12 sec." 



Incidentally we are surprised that the University Press of Glasgow should 

 print "sees.," "ozs.," "lbs.," etc. 



J. Wemyss Anderson. 



Optical Theories: based on Lectures delivered before the Calcutta University. 

 By D. N. Mallik, B.A., Sc.D., F.R.S.E. [Pp. vi + 181.] (Cambridge : 

 at the University Press, 191 7. Price js. bd. net.) 



In 1912 the author of this volume was appointed Reader in Physics in the Univer- 

 sity of Calcutta, and invited to deliver a course of lectures on Optical Theories. 

 One of the conditions attaching to this appointment was that the lectures were 

 subsequently to be published. It seems a pity that such a condition should be 

 laid down, and the matter of publication not left to the lecturer's discretion. In 

 the present instance there was already available Dr. Whittaker's excellent History 

 of the Theories of Aether and Electricity, published in 1910, which has rendered 

 such a volume as the one under review unnecessary. The present volume is, 

 indeed, considerably shorter than Dr. Whittaker's work ; but this is a doubtful 



