32 THE ICE AGE IN CANADA. 



changes of the relative levels of sea and land must be 

 taken into account in explaining the distribution of 

 marine clays and sands, boulder deposits, etc., which are 

 often regarded with reference to the present levels of the 

 country, or as contemporaneous deposits without regard 

 to their elevation, a method certain to lead to inaccurate 

 conclusions. 



The Saxicava sand (b) indicates shallow-water condi- 

 tions with much driftage of boulders, and probably glaciers 

 on the mountains. It constitutes in many districts a 

 second boulder formation, and possibly implies a some- 

 what more severe or at least more extreme climate than 

 that of the upper Leda clay. Terraces along the coast 

 mark the successive stages of elevation of the land in and 

 after this period. There is also evidence of a greater 

 elevation of the land succeeding the time of the Saxicava 

 sand, and preceding the modern era.* 



It is well known that very diverse theoretical views 

 exist among geologists as to the origin of the deposits 

 above referred to. The conclusions which have been 

 forced upon the writer by detailed studies extending over 

 the last forty years, are that in Canada the condition of 

 most extreme glaciation was one of partial submergence, 

 in which the valleys were occupied by a sea laden with 

 heavy field-ice continuing throughout the summer, while 

 the hills remaining above water were occupied with 

 glaciers, and that these conditions varied in their distri- 

 bution with the varying levels of the land, giving rise to 

 great local diversities, as well as to changes of climate. 

 There seems to be within the limits of Canada no good 

 evidence of a general covering of the land with a thick 



* Supplement to Acadian Geology, 3rd edition, pp. 14, et seq. 



