REVIEWS 399 



that the book is likely to prove a useful one in institutions where brief 

 courses in geology are taken b}' somewhat mature students. 



The book perhaps departs as much and as satisfactorily from the 

 text-books heretofore in use, in its treatment of the later parts of his- 

 torical geology, as at any point. In his treatment of the Mesozoic and 

 later periods, the author has brought together much data not hereto- 

 fore incorporated in a text-book, and his handling of that difficult 

 part of the subject is much more satisfactory than that found in most 

 text-books of corresponding scope. 



The illustrations in the volume are mainly new and attractive, many 

 of them being reproductions from photographs direct. The illustra- 

 tions of fossils seem to have been selected with great care, but are, on 

 the whole, fewer in number than could have been wished. 



The publishers have done their usual excellent work in the prepa- 

 ration of the volume. R. D. S. 



Missouri Geological Survey, Vol. XI; Clay Deposits. By H. A. 

 Wheeler. 622 pp., 39 pi. Jefferson City, 1896. 



The eleventh volume issued by the Missouri Survey is well up to 

 the standard of the previous work. It is a report of much more than 

 local interest, and will doubtless become the standard book of reference 

 for clay workers, filling a position analagous to that of the Manganese 

 Report of the Arkansas Survey. The Missouri clay report is the most 

 comprehensive work treating this subject issued by any American state 

 since the New Jersey report of 1878. It monographs the subject of clays 

 and clay working as exemplified in the wide range of deposits and pro- 

 cesses in Missouri. It is written from the point of view of the engineer 

 and treats of the different clays as adapted to various uses. Never- 

 theless there are many geological problems whose solution will be 

 the easier for it. The large number of new analyses, as well as the 

 careful tabulation of a wide range of older ones is alone a feature of 

 great value. The physical tests, the studies of fusibility, plasticity, and 

 shrinkage, aside from their immediate practical importance, may be 

 used to advantage in studies of the origin of mountains and of moun- 

 tain-making forces. Probably few portions of geology are less under- 

 stood or more complex than that which relates to metamorphism, and 

 in order to understand the nature of metamorphic rocks it is necessary 

 to have somethinsr more than a ijeneral notion of the nature of the 



