Geology. 157 



1 1 . Magnetic Declination Tables and Isogonic Charts for 1902 ; 

 1>y T A. Bauer. 405 pp., 2 pis. Washington: United States 

 Coa^ Survey. — The increased demand for magnetic data has led 

 the Coast Survey to issue a book bringing down to date the prin- 

 cipal facts relating to the earth's magnetism and to construct new 

 magnetic charts. 



12. Manual of Advanced Optics ; by C. R. Mann. 193 pp., 

 39 figs. Chicago, Scott, Foresman & Co. — The greater practical 

 value of other branches of physics — electricity and magnetism for 

 example, has resulted in the development of these subjects far be- 

 yond that of optics in the average physical laboratory. It is, never- 

 theless, a fact that whether we consider the beauty of the mathe- 

 matical demonstrations or the accuracy of the measurements, no 

 subject can surpass optics for quantitative physical work. To 

 one who is interested in pure physics the little book just issued 

 by Prof. Mann will prove most welcome. It attempts to do for 

 optics what Carhart and Patterson's Electrical Measurements has 

 done for electricity. There are certain features which deserve 

 special mention. First of all, the logical arrangement of the 

 experiments is evident ; they grow one out of another as the 

 student is ready for them. The meaning of " resolving power " — 

 a somewhat mysterious term in the mind of most students — is 

 made perfectly clear when illustrated by the simple experiments 

 outlined in connection with it. Measurements in connection 

 with the phenomena of polarized light are clearly outlined 

 and are accompanied by helpful suggestions. The diffrac- 

 tion grating is developed from the conditions of maximum and 

 minimum illumination from light which has passed through two 

 parallel rectangular slits, aud two distinct methods of obtaining its 

 resolving power are described. But perhaps the best feature of 

 the work is its description of the Michelson interferometer. 

 When we consider that over sixty papers have been published, 

 embodying investigations with this apparatus, and about as many 

 more discussing these results, it is obvious that physicists have 

 here a most powerful instrument of research. Heretofore the 

 theory and use of this form of the interferometer was to be found 

 only in magazine articles and in foreign works — sources likely to 

 be unavailable for students' use. The book contains a few errors, 

 which a later edition can easily rectify. — J. S. S., Orono, Maine. 



II. Geology. 



1. United States Geological Survey. — The following publica- 

 tions have recently been issued : 



Twenty-second Annual Report, 1900-01, Pt. I. 452 pp., 

 58 pis., 52 figs. The Director's Report (pp. 1-207) shows in- 

 creased cooperation with the several states and with different 

 branches of the government service — insuring better work at less 

 expense; The appropriation for the year was $997,310, and the 

 increase in appropriation is shown in an increase in scope and 



