102 THK ICE AGE IN CANADA. 



few, noth on account of the conditions of deposit and the 

 solvent action of carhctn (hoxide in the cohl hotlom 

 waters of the ocean. Tiie only point wantinjj; to com- 

 plete the analogy would he that emhaying and detention 

 of drift-ice shown on our I'leislocene niaji, and l)y which 

 the old glacial age was aggravated lioth in Euro]>e and 

 North America. To [)roduce this would recpiire some 

 ditl'erential elevation of the hed of the Tacitic toward the 

 northern margin of the present area of ice-drift. 



