EEFEEEjSTCE to the antiquity oe man. 



401 



of 35 feet daily and a discharge of 21 miles of ice annually. There 

 are other ice-fjords of far greater breadth than those, such as the 

 Humboldt glacier, which is 60 miles broad. Looking at the map, 

 it seems not improbable that the breadth of ice-front to rock- front 

 of the whole coast may be in the proportion of 1 to 20. 



Supposing the quantity which rims off to be equalized throughout 

 the whole extent of coast, the fringe of ice which would pass off 

 from the land would be a of a mile in width annually, or a breadth 

 of 1 mile would take eight years to pass off. If the proportion should 

 prove greater, say 1 : 30, then it would take twelve years. In the 

 one case a sheet of ice 100 miles long and of the width of the cen- 

 tral ridge would require eight hundred, and in the other twelve 

 hundred years for its formation ; or, taking the length of the 

 maximum radius of the old ice-sheets, of which the Canadian high- 

 lands and the Scandinavian mountains formed the centre, at 500 

 miles, the time required to form this length of ice would be respec- 

 tively four thousand and six thousand years. 



This, however, is based only on one roughly approximate known 

 quantity. We have, on the per contra side, to allow for certain un- 

 known quantities. First, allowance has to be made for the difference 

 between the free eseape into the sea and the impeded progress of ice 

 over land with slight gradients. This resistance would, however, 

 be partly neutralized by the gradual building up of a great thickness 

 of ice in the central area, where in the Glacial epoch it attained a 

 thickness of from 5000 to 6000 feet * 



The mass of ice, projected outwards towards its circumference, 

 would, except where it met with contracted channels, roll over the land 

 as a viscid body with comparatively little rigidity and friction. When, 

 in the Glacial epoch, the great southern glaciers of the Alps flowed 

 down the steep and confined valleys opening upon the flat plain 

 of Lombardy, they deeply ploughed their channels, and pushed 

 before them for short distances enormous moraines : but in the 

 wide open tracts of the United States, of ISTorthern Europe, and the 

 south of England, where the ice met with little resistance and could 

 expand in other directions, there is, as a rule, an absence of moraines 

 and often of glacial striae. 



In the second place, there were, no doubt, seasonal fluctuations 

 which would retard the flow for lesser or greater periods. It is 

 asserted that in Europe there were interglacial periods during which 

 the ice disappeared from the surface for great lengths of time. 

 But either the evidence is insufficient or it points to slight temporary 

 effects, except in one case, which is of more importance, and on which 

 the greatest stress is laid, namely, that of Durnten in Switzerland. 

 There beds of lignite with mammalian remains are intercalated 

 between two glacial deposits. Admitting the fact that the lignite 

 rests on beds of undoubted glacial (ground-moraine) origin, and that 

 the trees grew on the spot where their stumps and remains are found, 

 it by no means follows, as contended, that because these trees are all 



* The American geologists also consider that the Canadian land then stood 

 considerably higher than now. 



