Septebibee 18, 1896.] 



SCIENCE. 



407 



pecially British phenomena, as possibly to be 

 tedious to this class. 



The author proposes to himself the avoidance 

 of the special advocacy of particular interpre- 

 tations, which he regards as the peculiar fault 

 of most treatises on the subject. He professes 

 to be a judge and not a lawyer, and in harmony 

 with this there is an obvious effort throughout 

 to be judicial in his attitude. The implication 

 of partiality on the part of most authors will 

 hardly be accepted by the admirers of ' The 

 Great Ice Age ' or of ' Handbuch der Gletscher- 

 kunde,' and the author's assumption of the 

 functions of a judge, meting out the unbiased 

 truth where specialists have failed, is embar- 

 rassed by the absence of that prolonged and 

 profound study which is usually regarded as the 

 prerequisite of the judicial ofl&ce. Dr. Bonney 

 has written chiefly on petrological subjects 

 during the past twenty years, although previ- 

 ous to this he had studied and written consid- 

 erably on glaciers. It follows from this long 

 devotion to a fascinating specialty that his 

 familiarity with the literature of glaciology is 

 not altogether intimate, and this finds repeated 

 expression throughout the book. Much of the 

 material is taken from compilations rather 

 than from original sources and errors of fact 

 and of reference are not infrequent. 



The work has an excellent tripartite plan, 

 proceeding from the existing evidence of ice 

 work in alpine glaciers and arctic and antarctic 

 ice sheets (Part I.), to the traces of the glacial 

 epoch ( Part II.), and thence to theoretical 

 questions ( Part III.). This logical scheme is 

 not closely adhered to however, and doubtless 

 wisely, in the main. The illustrations in the 

 first part are chiefly taken from the glacial 

 drift of the past, while there are no illustra- 

 tions of existing glaciers. In Part II. hypothe- 

 ses and interpretations form a notable portion 

 of the discussion. 



The relation of lake basins to glaciers receives 

 foremost attention under the head of Traces of 

 the Glacial Epoch. The author's bias is obvi- 

 ously unfavorable to much glacial excavation, 

 indeed he had previously announced the con- 

 clusion, based on observations near the ends of 

 certain alpine glaciers, that ice ' has practically 

 no power to excavate.' ' In the discussion tf 



the lakes and elsewhere he manifests a hospi- 

 tality to theories involving submergence. 

 Eskers are treated at a reasonable length and 

 are fairly described. Their origin is left more 

 indeterminate than needful. It may be accepted 

 as demonstrated that they are the direct product 

 of glacial drainage. The only legitimate ques- 

 tions remaining undecided relate to details of 

 special position and of relations to the ice. 

 The discussion of drumlins is brief and unsatis- 

 factory. The great phenomena of the till sheets 

 and of the marginal moraines are almost ignored 

 in the treatment of the traces of the glacial 

 epoch, though moraines of the alpine type are 

 frequently referred to in the discussion of the 

 present glaciers. 



Ice work in Great Britain is discussed with 

 much elaborateness, which will doubtless make 

 the work acceptable to the subjects of the 

 Queen, but will seem to American students, in 

 view of the limitation of the great deposits of 

 this continent to ten pages, somewhat dispro- 

 portionate. In the discussion of the American 

 formations the selection of matter is not all that 

 could be desired. There is no comprehensive 

 sketch of the great features of this greatest of 

 all glaciated regions. The map given is old and 

 borrowed from a popular work, and fails to rep- 

 resent the latest delineations, much less the 

 latest classifications. The map of the imaginary 

 Lake Ohio has no place in such a work. The 

 1,700-foot beach lines of Spencer are cited as 

 though unquestioned, though we think their 

 author would not now insist upon the correct- 

 ness of his identification. 



The third part opens with an interesting and 

 valuable discussion of the temperature of the 

 glacial epoch, in which it is maintained that a 

 very moderate fall of the average temperature 

 would suffice for the glaciation that occurred. In 

 discussing the probable causes of the glacial 

 epoch. Dr. Bonney points out at length the 

 difficulties that attach to all current hypotheses, 

 and concludes that a complete solution of the 

 problem is as yet undetermined, and in this we 

 think he is altogether correct. In the treatment 

 of the number of glacial epochs, the discussion 

 turns, not upon the number of subdivisions of 

 the Pleistocene glaciation (a subject much dis- 

 cussed in recent years), but on the number of 



