REVIEWS 723 



changes in stratigraphic classification and correlation, and especially 

 of the truth of his statement on p. 582 that "the separation of the history 

 of the earth into chapters should be based, not upon the unconformities, 

 however great, but upon the changes which life has experienced." There 

 may be disagreement with the theory of isostacy as explained on pp. 365 

 to 368 and applied on pp. 132, 472, 478, and 651. 



Little but praise should be expressed for the illustrations in the 

 book, for almost all of them are clear and well chosen. Most of them 

 are new, and this feature will be appreciated. There are, however, a few 

 mistakes connected with the illustrations. Fig. 103 pictures as a pene- 

 plain a surface which is now known not to be a peneplain. Figs. 142 and 

 145 seem to be misplaced; they do not illustrate the work of mountain 

 glaciers. Figs. 396 B and 414 B are both labeled " Receptaculites 

 ohioensis"; fig. 414 B illustrates R. oweni. The illustrations of various 

 principles described in words, which occur throughout the book, are 

 numerous, well chosen, and altogether laudatory. 



There is no general plan for presentation of references in the book. 

 Footnotes giving definite references on specific points are practically 

 wanting. A few general references are given at the ends of chapters 

 in Part I and at the ends of smaller divisions within chapters in Part II. 

 In some cases previously published material is quoted, with or without 

 the name of the author, but without specific reference. Much material 

 is taken from classic geological literature without reference; for instance, 

 material on the geomorphology of the Appalachian Mountains, Murray's 

 classification of marine sediments, metamorphism, the bar theory for salt 

 formation, and the Lafayette formation. The book would be of much 

 greater value as a work of reference if more care had been taken with 

 sources. 



As in the case of any such work, Professor Cleland's book has its 

 good points and its points of weakness, in which the good points out- 

 number and outweigh those of the opposite character. 



A. C. T. 



Mine Waters. By A. C. Lane. Ann. Rept., Board Geol. and Biol. 

 Surv. (191 1), pp. 774-779- 

 The study of mine waters in the copper district of northern Michigan 

 is of practical interest, first, owing to the effect on boilers of the admix- 

 ture of the lower strongly saline waters with those of upper levels; 

 secondly, because it seems clear that the character of the water has had a 

 considerable importance in the deposition of the copper. Observation 



