4 i4 PREHISTORIC EUROPE. 



But this, as we know, was not the case, for frontal moraines of 

 considerable size, although usually much worn and degraded, do 

 now and then occur at or near the mouths of many of the more 

 considerable mountain-valleys ; and the whole evidence would 

 lead me to conclude that the glaciers of late glacial times took 

 a very long time indeed to melt away, so as to allow of the 

 accumulation of great heaps of angular debris and morainic 

 gravels. Thus at the opening of the mountain-reaches of the 

 Tay valley below Dunkeld we encounter abundant heaps and 

 hummocks of morainic gravel, shingle, and boulders, which are 

 merely highly denuded frontal moraines, the general concentric 

 arrangement of which can yet be traced and mapped out. And 

 similar morainic gravels are noticeable at many other places 

 farther up the valley. It is not until we get to the heads of the 

 glens above Loch Tay that we encounter moraines which bear 

 every mark of a more recent origin. Now, did these well- 

 preserved moraines really pertain to the Glacial Period properly 

 so called, I should have expected to trace a gradual passage 

 between them and the more worn and wasted morainic heaps 

 farther down the valleys. Why, in walking up a long Highland 

 glen, should we almost invariably pass at once from highly-wasted 

 and denuded banks and heaps of morainic detritus to a series of 

 cones and ridges sprinkled with perched blocks, which look so 

 fresh that the glaciers which deposited them might have occupied 

 the upper valley-reaches only a few years ago ? There are two 

 answers which may be given to this query. It might be held 

 that the new-looking fresh moraines in the upper reaches of the 

 glens were deposited during the last stand made by the glaciers 

 at the closing period of the Ice Age ; the more perfect appearance 

 of the cones and ridges being accounted for, partly by the fact 

 that they were the last to be laid down, and partly also by 

 supposing that the attenuated glaciers which heaped them up 

 made a considerable pause at the heads of the glens before they 

 finally melted away. But while it may be admitted that the 

 moraines which were last to be deposited would necessarily show 

 less signs of age than those belonging to the time when the 



