REVIEWS 6S9 



The printing of V— i for V— i on p. 59 will not prove very intelligible to a lay 



OWt OWL 



man. In the footnote to p. 74, dsz is printed for ds"^, etc., and i — • — for i , 



the author appearing to have quoted formulae which he does not understand. 

 These are but a few examples, chosen from amongst many. 



The style in which the book is written is irritating : such sentences as 

 "Suppose yourself a worm — the Bible says you are, anyway"; "As- 

 tronomers, indeed, say that we are moving at tremendous speed towards 

 Canis Major — in other words, that the world is going to the dogs," are typical. 



Readers who require an elementary but accurate account of Einstein's 

 theory should leave this book alone and study the English translation of 

 Einstein's own elementary exposition (reviewed in a previous number) or 

 one of the other available volumes by an author of repute. H_ S. T. 



From Newton to Einstein. Changing Conceptions of the Universe. By 



Benjamin Harrow, Ph. D. [Pp. x -{- 95.] (London : Constable & Co., 

 1920. Price 25, 6d. net.) 



This volume does not claim to be an exposition of Einstein's theories. It 

 consists of a brief review of the conceptions of gravitation and the aether, 

 from the time of Newton to the present day, described in a readable manner 

 and free from serious inaccuracies. Newton's work is reviewed in some detail : 

 an account is then given of Huyghen's wave theory of light and its triumph 

 over the corpuscular theory. It involved the introduction of the conception 

 of the aether, which was strengthened by the epoch-making electromagnetic 

 theory of light, enunciated by Clerk-Maxwell. The modern developments — 

 the electron structure of matter, and the connection between electrical and 

 optical phenomena and the motion of electrons — are described. This leads 

 to the question whether, if matter and light have the same origin, and if 

 matter is subject to gravitation, why not light also ? So the author comes to 

 the 1919 ecUpse expeditions and thence to Einstein's theory and some of its 

 consequences. The essay should prove of interest to the lay-reader whose 

 curiosity has been aroused by the prominence accorded in the Press and 

 elsewhere to Einstein's theory. H. S. J. 



Geodesy, including Astronomical Observations, Gravity Measurements, and 



Method of Least Squares. By George L. Hosmer, Associate Professor 



of Topographical Engineering, Massachusetts Institute of Technology. 



[Pp. xi -\- 368, with 115 figures in text.] (New York : John Wiley & 



Sons ; London : Chapman & Hall, 1919. Price 185. 6d. net.) 



This introductory textbook on geodesy will prove valuable to English 



students of the subject. For some reason or other, the study of geodesy has 



been much neglected in this country, and there is no concise, complete and 



up-to-date textbook by an English author available. The neglect of the 



subject at the Universities in this country is probably responsible for the 



state of affairs, which the projected foundation of a Geodetic Institute at 



Cambridge — if realised — may do much to remedy. 



The author has struck a happy compromise between theory and practice. 

 Whilst the practical details are carefully explained (the methods used in the 

 U.S. Coast and Geodetic Survey being generally followed), the underlying 

 principles are clearly elucidated. The whole ground of geodesy is covered 

 in a concise manner — triangulation, gravity measurements, precise levelling, 

 and figure of the earth. The astronomical observations required for the 

 determinations of longitudes, latitudes, and azimuths are explained in sufficient 

 detail. In connection with this, no reference has been made to the use of 

 wireless time signals for the determination of longitudes. This is a serious 



