638 REVIEWS 



Glen Roy, ice-work in Great Britain and Ireland, and in Europe and 

 other parts of the world constitute the leading themes ; and Part III, 

 relating to theoretical questions, especially the temperature of the 

 glacial epoch, its possible causes, and the number of epochs. The 

 discussion of the temperature of the glacial epoch embraces the largest 

 amount of measurably unfamiliar material and is perhaps to be regarded 

 as the most valuable part of the book. The description of alpine and 

 polar glaciers is not brought up to date and is sadly lacking in suitable 

 illustrations, for which abundant material now exists. In the discus- 

 sion of the traces of the glacial epoch disproportionate attention is 

 given to the excavation of lake basins, to the exclusion of erosive work 

 in other lines quite as important, and the author's impartiality is not 

 as well sustained here as elsewhere. Very much attention is given to 

 the glacial phenomena of Great Britain, and relatively scant attention 

 to that of Europe and America. It is natural that an English writer, 

 presumably having in mind chiefly the English public, should give 

 much prominence to home phenomena, but obviously in a work which 

 takes on so comprehensive a title and is published as a part of an 

 international series, the distribution of attention should be somewhat 

 proportional to the development of the phenomena. In the discussion 

 of the possible causes of the glacial epoch the author's judicial 

 attitude appears to the best advantage. We think he is correct in 

 concluding that " the glacial epoch has not yet received any satis- 

 factory explanation." The literary style of the work is excellent, the 

 language being clear and quite free from rhetorical coloration. The 

 illustrations are not only scant and poor, but the selection is unfortu- 

 nate in several cases, some of them being unworthy of reproduction. 



T. C. C. 



General Relations of the Granitic Rocks in the Middle Atlantic 

 Piedmont Plateau, by G. H. Williams. (Fifteenth Annual 

 Report, U. S. Geol. Surv., pp. 657-684.) 



The Piedmont plateau is classic ground in American geology. 

 Within its limits many of the important problems of American science 

 have been worked out, but by far the larger number of questions 

 which it presents are yet unanswered. It is a region of great com- 

 plexity. From tl\^e holocrystalline, undoubted igneous masses of the 

 eastern border to the unchangred sedimentaries further west there is 



