October 28, 1898.] 



SCIENCE, 



599 



sion of polarization currents, Faraday's law, 

 ion transference, preliminary experiments, etc. ; 

 and the concluding chapter discusses the con- 

 struction and calibration of instruments, such 

 as the tangent galvanometer and those used 

 for measuring pressure and regulating resist- 

 ance. Tables of electro-chemical equivalents 

 of the more important elements, of thermo- 

 chemical data, and of wire resistance, are ap- 

 pended. 



The second book, as its title implies, is in 

 part of a more practical character. The first 

 forty pages are given again to a discussion of 

 instruments, but the remainder is devoted to a 

 •discussion of simple electro-chemical experi- 

 ments, such as electrolysis of hydrochloric acid 

 with and without a diaphragm ; electrolysis of 

 dilute sulphuric acid, or sodium hydroxide, 

 with a diaphragm ; formation of persulphuric 

 acid by the electrolysis of sulphuric acid ; pre- 

 cipitation of copper under different conditions ; 

 precipitation of magnesium from a fused salt of 

 the metal ; the number of processes involved 

 being sufficient to give some idea of electro- 

 ■chemical operations. 



The final chapter, on 'Organic Electrolysis,' 

 was written by Professor Elbs and is one of the 

 most interesting chapters in the book. In a 

 very few experiments it gives some idea of the 

 application of electrolysis to organic chemistry, 

 an idea which is, however, greatly enlarged by 

 such a work as the third volume of Peters' 

 'Angewandte Elektrochemie.' 



The translation by Professor Smith is espe- 

 cially welcome, not simply because of his skill 

 in such work, but since it comes from the lead- 

 ing authority in practical electro-chemistry in 

 America. 



_^ H. C. J. 



SCIENTIFIC JOURNALS. 

 The Journal of Geology, May-June, 1898 : 

 The number opens with 'A Symposium on the 

 •Classification and Nomenclature of Geologic 

 Time-Divisions,' a contribution that is based on 

 a series of fourteen questions that had been sub- 

 mitted to the geologists mentioned below. The 

 questions involve a discussion of the extent to 

 which subdivision should be pursued in the 

 >time and physical scales, and of the number of 



geological periods (as the word period was used 

 by the Berlin Congress) which it is desirable to 

 adopt. Considerable difference of opinion is 

 developed, so much so as to make the average 

 teacher impatient with this continual tinkering 

 with words. Opinions are expressed by Joseph 

 Le Conte, G. K. Gilbert, W. B. Clarke, S. W. 

 Williston, Bailey Willis, C. R. Keyes and 

 Samuel Calvin. ' Probable Stratigraphical 

 Equivalents of the Coal Measures of Arkansas,' 

 by C. R. Keyes. The author cites the great 

 thickness of the Arkansas Coal Measures as 

 compared with those of Iowa and Missouri, 

 i. e., 2,400 feet as against 500-600, and strongly 

 opposes the ordinary conception of the Ozark 

 island of Carboniferous and later time. He 

 emphasizes the evidence that land conditions 

 followed the deposition of the St. Louis lime- 

 stone and preceded the formation of the Iowa 

 and Blissouri Coal Measures. He explains the 

 greater thickness of the Arkansas measures by 

 their continuity of deposition without regard to 

 this change on the north. A paper ' On the 

 Origin of certain Siliceous Rocks ' is presented 

 in two parts. The first, by O. A. Derby, con- 

 tains 'Notes on Arkansas Novaculite,' and 

 gives the results of an investigation of the no- 

 vaculite by crushing it to slimes without destroy- 

 ing the larger included grains of secondary 

 quartz. The slimes were then studied with the 

 microscope, and the author reached the con- 

 clusion that an origin by replacement of cherty 

 limestone has great claims to confidence. J. 

 C. Branner, in the second part, comments on 

 these results and systematically reviews the 

 explanations that have beeen advanced for the 

 siliceous rocks. He adds a few notes on those 

 in California. 'A Study of Some Examples of 

 Rock Variation,' by J. M. Clements, deals with 

 an interesting series of eruptives at Crystal 

 Falls, Mich., which follow the Upper Huronian 

 and precede the Potsdam. The series consists 

 of quartz-diorite, hornblende-gabbro, bronzite- 

 norite and peridotite, and is described in detail 

 with analyses. The hornblende-gabbro was 

 first in time; then came the norite and perido- 

 tite, and, last of all, the diorite with transitions 

 into granite. Under the ' Studies for Students ' 

 a good brief review of the development and 

 geological relations of the fishes is given by E. 



