286 Scientific Intelligence. 



tives. The table of contents is followed by a convenient list of 

 the 20 tables of physical constants which are distributed through- 

 out the volume. 294 problems, with the numerical answers given, 

 are placed immediately after the explanations of the principles 

 which they involve. 



Attention should be called to the fact that in certain minor 

 details the authors diverge from custom, just as the above quota- 

 tion shows that they have done in the arrangement of the general 

 subject-matter. For example, speed and velocity are differen- 

 tiated respectively by the symbols v and v. Formulae for 

 uniformly accelerated motion are written with double signs, as 

 " s = v t ± at * / 2 ", thus giving to " a " an arithmetical rather 

 than an algebraic significance. The same preference for arithmetic 

 over algebra is emphasized by the authors' italics in the follow- 

 ing sentence of page 417: "The potential, due to all the charges, 

 is simply the arithmetical sum of the potentials due to the in- 

 dividual charges." h. s. u. 



II. G-EOLOGY AND MlNERALOGY. 



1. The Geology of the Lake Superior Region ; by Charles 

 Richard Van Hise and Charles Kenneth Leith. Monograph 

 LII, United States Geological Survey. Pp. 641, pis. xlix, figs. 76. 

 Washington, 1911. — This work brings into one volume the results 

 of the studies which have been carried forward since the organi- 

 zation of the national survey. The great economic value of the 

 region, its structural complexity, and the absence of fossils have 

 resulted in concentrating upon it probably a greater amount of 

 study than upon any other area of similar size in the world. 

 There is displayed, furthermore, an unusually complete succession 

 of pre-Cambrian rock systems reaching back to the Archean, 

 making the region one of high general and theoretic as well as 

 economic interest. The authors, who more than any other men 

 have advanced the knowledge of Lake Superior geology, have 

 completed an admirable piece of work in this volume. In it is 

 not only collected a resume of the descriptive geology of the vari- 

 ous districts, but there is given also a discussion of the genesis of 

 the iron, copper, and silver ores and the conditions of sedimen- 

 tation which prevailed through the successive periods. 



The region which is discussed embraces about 181,000 square 

 miles and is accompanied by a general geological map on a scale 

 of 1 to 1,000,000. In an enumeration of certain features of the 

 volume, attention should be called to Chapter IV, Physical Geog- 

 raphy of the Lake Superior Region, by Lawrence Martin, which 

 deals with the several baselevels of erosion, the resulting relief, 

 and the origin of the present Lake Superior Basin. Chapters V 

 to XIV inclusive give the geology of the several iron districts. 

 Chapter XV contains sixty-one pages on the Keweenawan series. 



