Geology and Mineralogy. 563 



the effects of the electric current and with magnetism. The titles 

 of the remaining chapters are respectively, — " Chemical Effect of 

 the Electric Current," " The Heating Effect of the Electric Cur- 

 rent," "Induced Electromotive Force," and "Electric Charge 

 and the Condenser." In addition to the lucid explanations the 

 ideas are made very vivid and concrete in two ways, first, by 

 placing diagrams of the mechanical or hydraulic analogues side 

 by side with the diagrams of the associated electric or electro- 

 magnetic apparatus, and second, by tabulating the statements of 

 analogous laws and facts in parallel columns. The experiment 

 with the "electric doubler" (Art. 108), is especially interesting 

 and instructive. About 120 problems, with answers, are appended 

 to the several chapters. In conclusion it may be remarked that 

 there is a frankness of statement and freshness of presentation 

 which should prove stimulating to the teacher as well as to the 

 student. h. s. u. 



II. Geology and Mineralogy. 



1. The Climatic Factor, as Illustrated in Arid America ; by 

 Ellsworth Huntington, Assistant Professor of Geography in 

 Yale University ; with contributions by Charles Schuchert, 

 Andrew E. Douglass, and Charles J. Kullmer. Pp. vi, 341, 

 with 12 plates, 2 maps, 90 text-figures. Carnegie Institution of 

 Washington Publication No. 192, 1914. — This is a volume 

 replete with new data and new points of view, bearing upon the 

 fields of archeology, history, meteorology, and geology. It is 

 divided into three parts. Part I deals with the problem of cli- 

 matic changes, divided into a discussion of the data which show 

 the nature of the changes during the past 2,000 to 3,000 years, 

 and the hypotheses which are suggested in order to give an ade- 

 quate explanation of the phenomena. There are twenty chapters. 

 Part II is a single chapter of thirty pages by Professor Schuchert 

 on the climates of geologic time. Part III consists of tables. 



To revert in more detail to Part I, the first three chapters give 

 an account of the climatic character of Arizona and New Mexico 

 and its relations to the physiography and vegetation. Then fol- 

 lows Chapter IV on the climatic theory of terraces and the means 

 of distinguishing terraces of climatic origin from those due to 

 crustal movements. This is a most important subject as it is the 

 key to the climatic interpretation of the Pleistocene and recent 

 epochs in regions of piedmont alluvial deposits. It is a relatively 

 new principle which has been but little used and is not as yet 

 widely understood. The fluctuations of the inclosed bodies of 

 water furnish supplemental evidence. Chapters VI to IX 

 inclusive deal with the archeological evidence. Taken in connec- 

 tion with the preceding chapters, they go to show that notable 

 changes in the mean annual rainfall have occurred since man first 



