Chemistry and Physics. 61 



of the three American Commissioners : Dr. G. N. Lewis, the 

 Massachusetts Institute of Technology, Boston, Mass. ; Professor 

 G. F. Hull, Dartmouth College, Hanover, N. H., and Professor 

 J. Stieglitz, the University of Chicago, Chicago, 111. After Jan. 

 15th, 1912 the price of the volume is likely to be increased. 



9. The Sun ; by Charles G. Abbot. Pp. xv, 448 ; 26 plates, 

 72 figures. New York, 1911 (D. Appleton & Company). — A nota- 

 ble work which every student of physics and of astronomy will 

 find of absorbing interest. It is the first considerable book bear- 

 ing its title since that of Professor C. A. Young, so usefully and 

 widely known, published just thirty years earlier ; and it is pleas- 

 ing to find that its frontispiece, like that of its predecessor, is a 

 reproduction of S. P. Langley's famous drawing of a typical sun- 

 spot, unfortunately somewhat marred, however, by a partial fill- 

 ing of the nucleus of the spot. This is to be regretted because too 

 many contemporary readers will get an inadequate impression of 

 the merit of the wonderful original drawing. 



It is impossible in a brief review to do more than indicate in 

 the most cursory manner some of the important advances in astro- 

 physics which are here admirably set forth. The first five chap- 

 ters cover much the same ground as Young's treatise, with 

 amplified and modernized discussion of methods for determining 

 the radiation of the sun, together with excellent reproductions of 

 some of the most significant spectroheliograms from the Mt. 

 Wilson observatory. Of the remaining five chapters, the seventh, 

 — The sun as the earth's source of heat — and the tenth — The sun 

 among the stars — perhaps contain the greater number of modern 

 additions to knowledge which would interest a philosophical 

 reader ; but the chapter giving a succinct history of the efforts of 

 inventors to utilize solar energy is interesting and valuable. The 

 excellence of the reproductions of recent photographs of nebulae 

 should not pass unnoted. c. s. h. 



10. Physical Optics ; by Robert W. Wood. Pp. xvi, 705 ; 2 

 plates, 399 figures. New York, 1911 (The Macmillan Company). — 

 This is a second and enlarged edition of the work reviewed at 

 length in this Journal (see vol. xxii, p. 193, 1906). The additions 

 in this volume are -material both in quantity and in importance ; 

 of these the last chapter, on the principle of relativity, may be 

 especially named on account of its interest. c. s. h. 



11. Illumination, its Distribution and Measurement ; by 

 Alexander Pelham Trotter. Pp. xvii, 292 ; 209 figures. Lon- 

 don, 1911 (Macmillan & Co.) — The frontispiece is a reproduc- 

 tion of a portrait by Perroneau of Pierre Bouguer, "the father of 

 photometry," to the memory of whom this volume is dedicated. 

 This book is an expansion of a paper which, on May 10, 1892, 

 was read before the Institution of Civil Engineers and which was 

 first published in volume ex of the Proceedings of the Institution. 

 The paper was subsequently rewritten and it then appeared in 

 The Illuminating Engineer. 



The subject matter is divided into three parts. The first deals 

 with the primary and derived units of light, with the theory of 



