Geology and Mineralogy. 71 



Chapters on the characters of glaciers, their distribution, with 

 descriptions of occurrences in North America, lead up to the dis- 

 cussions of the glacial period, its varied results, and possible 

 cause. Considerable new matter has been added in supplement- 

 ary statements. The author gives the different hypotheses that 

 have been advanced to account for the formation of the great ice- 

 sheets, and discusses some of them at length. Croll's hypothesis 

 is now so generally disregarded, or relegated to a minor position, 

 that it hardly seems worth the extended treatment given to it. It 

 is here that the work suffers in clearness of presentation to the 

 general reader, caused b}' the retention of the older matter and 

 the interspersal of new. An entire rewriting of this part would 

 have greatly aided it. The author comes to no definite conclu- 

 sion as to the cause of the glacial period, but considers it is a 

 problem for the future. 



Perhaps that part of the work which will continue to meet the 

 most criticism is the final portion in which the age of man in this 

 country is treated. As is well known, Professor Wright is an 

 advocate of the human occupancy of North America during the 

 glacial epoch. The arguments of the evolutionists he considers 

 met hy the great recency which he attributes to this period. It 

 is not, however, the point of view but the treatment of evidence 

 in which the writer must meet objection. Apparently all finds 

 of underground human remains and implements, under any cir- 

 cumstances, have to him scientific value, and the criteria applied 

 in other portions of the book, in considering alternative expla- 

 nations, here seem to be largely wanting. The age of man in 

 this country is still an open question, and it will not be settled to 

 the satisfaction of scientists until a sufficient body of evidence has 

 been produced by men whose training, both in geology and 

 archaeology, renders them thoroughly competent to undertake the 

 necessary investigations, and to recognize the true value and 

 relations, in place, not of a part, but of all the facts. l. v. p. 



5. Characteristics of Existing Glaciers; by William Her- 

 bert Hobbs, Professor of Geology in the University of Michigan. 

 Pp. xxiv, 301; 34 plates, 140 figures. New York, 1911. The 

 Macmilian Co. Price, $3.25 net. — This work easily takes rank 

 among the most important treatises on glaciation, and it is further- 

 more made attractive by good paper, clear topography, and hand- 

 some illustrations. The plates are half-tone reproductions of 

 instructive photographs, and the line drawings are very effective 

 in imparting graphic ideas beyond the reach of the camera. It is 

 a study of existing glaciers with the emphasis placed upon the 

 glacier as a whole and the relative function of each part, rather 

 than, as in most previous works, a detailed treatise of such sub- 

 jects as glacial motion or glacial erosion. The glacier is further- 

 more studied from the standpoint of its life history, from its incep- 

 tion in a gathering snowfield through the cycle of its growth and 

 retreat to its ultimate extinction. From this rather new concept, 

 however, definite ideas are derived on such debated topics as 



