268 THE STORY OF THE EARTH AND MAN. 



towards the equator than the latitudes indicated, we 

 do not find the proper drift deposits; but merely 

 weathered rocks or alluvia, or old sea bottoms raised 

 up. This limitation of the drift, at the very outset 

 gives it the character of a deposit in some way con- 

 nected with the Polar cold. Besides this, the general 

 transport of stones and other material in the northern 

 regions has been to the south; hence in the Northern 

 Hemisphere this deposit may be called the Northern 

 Drift. 



If now we take a typical locality of this formation, 

 such, for instance, as we may find in Scotland, or 

 Scandinavia, or Canada, we shall find it to consist of 

 three members, as follows : 



3. Superficial Sands or Gravels. 



2. Stratified Clays. 



1. Till or Boulder Clay. 



This arrangement may locally be more complicated, 

 or it may be deficient in one of its members. The 

 boulder clay may, for example, be underlaid by 

 stratified sand or gravel, or even by peaty deposits ; 

 it may be intermixed with layers of clay or sand ; the 

 stratified clay or the boulder clay may be absent, or 

 may be uncovered by any upper member. Still we 

 may take the typical series as above stated, and in- 

 quire as to its characters and teaching. 



The lower member, or boulder clay, is a very 

 remarkable kind of deposit, consisting of a paste 

 which may graduate from tough clay to loose sand, 



