Geology and Mineralogy. 251 



two hundred pages are occupied with a general description of the 

 phenomena of optics with their mathematical theory. Chapters 

 iv, v and vi, on interference of light, diffraction, and diffraction 

 gratings, respectively, are especially good. The chapter on the 

 theory of optical instruments, however, leaves much to be de- 

 sired ; the theory of the microscope is not touched upon, and a 

 theory of the telescope, which leads to the conclusion that a mag- 

 nification of eight to the inch of aperture of the objective quite 

 exhausts its resolving power for an eye free from spherical aber- 

 ration, is necessarily erroneous. 



Part II, on modern theories of light, of dispersion and absorp- 

 tion, and of the relations of optical to electromagnetic phe- 

 nomena, containing all that is very recent in optical science, is of 

 greater value and interest. A careful reading of this portion is 

 certain to be profitable to every student of physics. The treat- 

 ment of Talbot's Bands (p. 329) may be cited as specially inter- 

 esting and suggestive. 



The illustrations of the work are not wholly satisfactory, with 

 the exception of its two plates which are reproductions of direct 

 photographs of interference phenomena. Unfortunately, the 

 references in the text to these plates contain many errors which 

 would prove very confusing to one not already familiar with the 

 phenomena. We may add that the first figure on Plate I, show- 

 ing the interference bands formed by a biprism, owes its irregu- 

 larities to a defective prism, not, as is asserted in the text, to the 

 periodic nature of light itself. c. s. h. 



19. Das Elehtrische Bogenlicht ; seine JEJntwickelung und 

 seine physikalischen Grundlagen / von W. B. von Czudno- 

 chowski. Erste Lieferung, pp. viii, 98. Leipzig, 1904 (S. 

 Hirzel). — The first part of this work upon the electric arc light 

 was issued some months since and is largely devoted to the phys- 

 ical side of the subject. The entire work is to be published in 

 six similar parts, and from what we have before us may be 

 expected to satisfy all demands as to fulness of description and 

 illustration. 



II. Geology and Mineralogy. 



1. A Treaties on Metamorphism ; by Charles Richard Van 

 Hise, TJ. S. Geological Survey, Monograph XLVII, 1286 pp., 13 

 pi., 32 figs. — Professor Yan Hise's Treatise on Metamorphism 

 will undoubtedly take rank as one of the most important single 

 publications ever issued by the Geological Survey. The volume 

 is the outcome of a life-long study in the province of metamor- 

 phic geology. Partial views have been published in his earlier 

 papers, and the ground work of metamorphism has, of course, 

 been gradually established through the labors of many leaders in 

 geology during the past century. Nevertheless the subject is 

 doubtless indebted to Yan Hise more than to any other one indi- 

 vidual for its reduction to an exact science. In the present* trea- 

 tise a highly successful attempt has been made to arrange the 



