274 Reviews — Sir J. W. Daioson — Canadian Ice- Age. 



is the mode actually followed by nature ; and that the hypothesis 

 I advocate is not nature's mode of action. I submit that when 

 chlorite and biotite are found together in the same rock, under the 

 circumstances stated by Dr. Callaway, that it is more in harmony 

 with the probabilities of the case to believe that the hydrous chlorite 

 was created by aqueous agencies after the intrusion of the granite 

 than to believe that the chlorite was created before the intrusion ; 

 that the biotite was formed out of a portion of the chlorite ; and 

 that during the long ages that succeeded, aqueous agencies (contrary 

 to our ordinary experience) either had no access to these rocks, or 

 that (contrary to their known habit) they altogether failed to form 

 any chlorite out of the unstable basic minerals exposed to their 

 ravages. 



I^ E AT" I IB AA7" S. 



I. — Peter Eedpath Museum, McGill University, Montreal, 

 October, 1893. The Canadian Ice-Age; being Notes on the 

 Pleistocene Geology of Canada, with especial reference to the 

 Life of the Period and its Climatal Conditions, and Lists of 

 the Specimens in the Museum. By Sir J. William Dawson, 

 C.M.G., LL.D., F.R.S., F.G.S., etc. 8vo. pp. 301, with 25 Illus- 

 trations. (Montreal, William V. Dawson ; New York, Scientific 

 Publishing Company. 1893.) 



SIR WILLIAM DAWSON states that for thirty years he has 

 aspired to make Canada as typical a region for the study of 

 the Pleistocene period, as Sir William Logan made it typical for 

 the Laurentian rocks. His guiding principles are briefly expressed 

 in convictions that the phenomena of the Glacial period are to be 

 explained by more active and extensive operation of the ordinary 

 causes still existing in more northern regions ; that there has not at 

 any time been a Polar ice-cap or great continental ice-sheets ; and 

 that the astronomical theory of glacial cold is incapable of fully 

 explaining the facts ; but that the cold climate was mainly a result 

 of geographical conditions involving a diiferent distribution of 

 ocean currents, and extreme local evaporation and condensation, 

 giving rise to local glaciers of great volume and to floating ice. 

 It is inferred that the close of the Glacial period cannot have 

 antedated by many centuries or milleniums the first appearance 

 of man as known in history. 



The book is divided into seven chapters. The first chapter is 

 chiefly a series of quotations mainly from the author's writings, 

 chosen to illustrate the principles with which he starts. 



The second chapter discusses the succession of deposits ; which 

 comprise a Lower Boulder-clay, with some travelled boulders and 

 a few Arctic shells ; succeeded by the Lower and Upper Leda-clay, 

 with marine shells and drift-plants ; and an Upper Boulder-clay, 

 including sand with Saxicava and gravel. These deposits are 

 found in the Lower St. Lawrence, the north shore of Lake Ontario, 



