REVIEWS 773 



Astronomy. A popular handbook. By Harold Jakoby, Professor of Astronomy, 

 Columbia. [Pp. xi + 435, with 32 plates and many figures in the text.] 

 (New York : The Macmillan Co. Price 10^. 6d. net.) 



In the preface to this volume the author states that it has been written primarily 

 for " the ordinary reader who may desire to inform himself as to the present state 

 of astronomical science, or to secure a simple explanation of the many phenomena 

 constantly exhibiting themselves in the Universe about him." Such a reader will 

 find the second of these desires amply satisfied by this book, the greater part 

 of which is occupied with elementary and lucid explanations of some of the 

 problems of spherical and gravitational astronomy. The explanation of the 

 differences between sidereal, true solar, and mean solar times, of the principles 

 of the sundial, of the methods of determination of the shape, size, and mass of the 

 earth and of the shape and dimensions of its orbit, and of the differences between 

 the Julian and Gregorian calendars are given. The methods by which the masses 

 and distances of the sun, moon, and planets have been determined are described, 

 as are also the methods by which the position of a ship at sea may be found. The 

 phenomena of the precession of the equinoxes, and of the librations of the moon, 

 and the causes of the production of tides, eclipses, and kindred phenomena are 

 also expounded in a simple manner. The variety of the subjects here mentioned 

 will sufficiently indicate the comprehensive nature of this portion of the book. 

 Wherever possible, the derivations of the mathematical results which are assumed 

 in the course of the arguments are given for the benefit of those readers who 

 possess a knowledge of elementary mathematics, these elementary explanations 

 being collected together separately in an appendix. 



The portion of the book dealing with descriptive astronomy is not nearly so 

 successful, being very sketchy, incomplete, and disjointed ; and the author would 

 have succeeded better had he not attempted to cover so much ground. The 

 beginner who may wish to study this part of the subject is recommended to turn 

 to other books where it is treated in a much more satisfactory manner. 



The author also intended that this volume should serve as a text-book for high 

 schools and colleges. It does not appear to be suitable for this purpose : much 

 is included that would be beyond the grasp of young students, whilst in the case 

 of more advanced students, the subjects here dealt with can be studied to much 

 greater advantage by a more free use of mathematics. The requirements of the 

 student are so different from those of the ordinary reader that it is impossible 

 to meet adequately the needs of both by one and the same volume. 



A few incorrect or misleading statements may be mentioned. On p. 125 it is 

 asserted that " so far as gravitational forces alone are concerned, the solar system 

 may endure for ever." The researches of Henri Poincare have negatived this 

 conclusion, which Laplace and Poisson erroneously believed to follow from their 

 mathematical investigations. On p. 181 the lunar mountains are stated to be from 

 1,000 to 2,000 feet high, whereas some of the large mountain rings rise to ten 

 times this amount. Also on p. 240 the velocity of light is given as 186,000 miles 

 per sec, whereas on p. 333 the value 183,000 miles per sec. is used. 



H. S. J. 



Die Physik der bewegten Materie und die Relativitatstheorie. By Max B. 

 Weinstein. [Pp. xii + 424.] (Leipzig: Johann Ambrosius Barth, 191 3. 

 Price 17 marks ; bound, 19 marks.) 



This book gives a careful and laborious account of the work done on electro- 

 dynamics in recent years, divided into two parts, the first presenting the pre- 



