CORRYS WITH OR WITHOUT LAKE-BASINS. 133 



pheric influences which is brought down to the sea is 

 at first left on the " ice-foot," or belt of ice fringing 

 the coast-line, to be afterwards, when that breaks 

 up, carried away and deposited in mid-ocean; con- 

 sequently, in such regions, there can be no natural 

 breakwater formed, but the coast must be left open 

 to the full action of the waves and marine currents. 

 In such places, therefore, marine denudation ought 

 to be more active than elsewhere. 



Let us now consider the temperate zones. Here 

 all of the denudants do some work; none of them, 

 however, being at the maximum or minimum of effi- 

 ciency, as the principal working powers, heat and cold, 

 under which all act, cannot reach their extreme inten- 

 sities. There is, however, some little work done by 

 each, more or less considerable in accordance with the 

 varied circumstances under which they act. Hence it 

 would seem that atmospheric influences perform their 

 maximum of work in tropical climates, and their mini- 

 mum in arctic regions ; on the other hand, both marine 

 and ice action accomplish their maximum of work in 

 arctic regions, and their minimum in the tropics. 



Let us now consider the conditions under which 

 larconnaught formerly existed. Here, as well as over 

 the whole of the North of Europe, an arctic climate 

 prevailed at the beginning of the glacial period, 

 and the efficiency of marine action must have been 

 considerably greater than at present ; to which add 



