518 Scientific Intelligence. 



struction of the large engine for ruling diffraction gratings and 

 of the 100-inch reflector is indicated. It is estimated that this 

 gigantic telescope will reveal about 100,000,000 faint stars hitherto 

 unobservable. Among the problems under investigation may be 

 mentioned solar meteorology, the brightness, motions, distances, 

 and evolution of the stars, the scattering of light in space, and 

 the magnitude and structure of the universe. All of the figures 

 are good, the photographs of spiral nebulae being especially attrac- 

 tive. The author's style and the subjects presented are of such a 

 nature that the reviewer could not lay the book aside until he 

 had read it through. h. s. u. 



11. The Electrical Nature of Matter and Radioactivity; by 

 Harry C. Jones. Third edition. Pp. ix, 212. New York, 1915 

 (D. Van Nostrand Co.). — A careful comparison, page by page, of 

 the first edition (see this Journal, vol. xxi, p. 4(35, 1906) with the 

 third shows that the original text has been kept unaltered as far 

 as possible. The comparatively slight changes introduced were 

 necessitated by the conscientious and successful endeavor to bring 

 the experimental data and theoretical considerations up to date. 

 The number of chapters has been reduced by unity by incorporat- 

 ing some of the material from chapter XVIII of the first edition 

 in chapter XVII of the third. The total number of pages has 

 been kept constant by abbreviating the index. It is pleasing to 

 note that this admirably written, semi-popular text has been so 

 well appreciated as to cause it to pass through three editions in a 

 relatively short period of time. h. s. u. 



12. The Book of Wireless / by A. Frederick Collins. Pp. xv, 

 222, with 219 figures. New York, 1915 (D. Appleton and Co.). 

 — In this extremely elementary book the author has endeavored 

 to anticipate and answer all reasonable questions which may arise 

 in the minds of boys or young men who are attempting to assem- 

 ble and operate either bought or home-made wireless-telegraph 

 sets. He even goes so far as to say: "But if you should have 

 any trouble and if any questions should come up which puzzle 

 you, if you will write to me, I shall gladly do all I can to help 

 you." 



The text is divided into three Parts having the following titles : 

 I. "A Small Wireless Outfit" (five chapters), II. "A Long Dis- 

 tance Wireless Set " (four chapters), and III, "Induction Coil, 

 Transformer and Electrolytic Interruptor" (three chapters). The 

 diagrams are large and clear, and the linear dimensions are indi- 

 cated whenever necessary. At the end of each chapter are given 

 itemized cost lists of parts for both commercial and home-made 

 sets. The last chapter of the volume relates to government rules 

 and regulations, examinations, etc. This is followed by several 

 appendices on wire gauges, drills, types of aerials, etc , a glossary, 

 and an index. The subject matter seems to be very well pre- 

 sented to meet the requirements of the readers for whom it was 

 written. h. s. u. 



