668 



PE0E. T. jtf'KENNY HUGHES OX THE ANCIENT 



man "who saw them, " some old stone things, hammer-heads and 

 heads of spears, and such like." So it is probable that this boulder 

 was in disturbed ground. 



Setting aside, then, any suggestion of ice-action arising out of the 

 character and position of these boulders, there does not appear to be 

 any satisfactory evidence of glacial conditions in Devonshire. Its 

 deep combes tell of long continuous erosion by the streams which have 

 cut their way back from the coast almost horizontally into the table- 

 land, not vertically clown from the tableland to sea-level. After the 

 rapids or waterfalls where the work is going on have receded, the 

 talus gathers in every hollow and on every ledge, and the enormous 

 thickness of the rainwash and run-of-the-hill in Devonshire tells of 

 long- continued subaerial waste. The thin laminse due to cleavage 

 or bedding, or both, are all, so far as I have seen, turned over down 

 the slope by gravitation, and none curve over in unexpected direc- 

 tions as if pushed by ice. There is nothing in the form of the 

 ground or the character of the superficial deposits (saving always the 

 boulders in question) to suggest ice-action. 



The thick deposits of subaerial talus do not differ in character 

 from those now being formed, and represent, not so much the 

 greater intensity of the cold at some former period, as the greater 

 length of time during which the surface has been exposed to the 

 disintegrating effects of weather, just like what prevails there still. 



The brown clays and other similar deposits referred to by 

 Mr. Hooker as possibly of glacial origin are obviously not to be 

 referred to the direct action of ice. They are not, as they stand, 

 Boulder-clays or true glacial deposits ; and if they are only due to the 

 destruction of old Boulder-clays, we are opening up another question, 

 viz. How far off were the Boulder-clays from which they were derived, 

 and to what denudation can those brown clays be referred? Did 

 it follow immediately upon the deposition of the moraine or when ? 

 It ma}^ be that Devon was under the sea during the age of extreme 

 glaciation in ~N.W. Europe, and received some of the marginal 

 glacial deposits and emerged early, so that all traces have been 

 destroyed. 



~No one can tell how far back we must place the beginning of the 

 subaerial denudation of this district. !N"or have we evidence to show 

 what was the condition of the surface of the great Devon plateau 

 when first it emerged from the sea. That no blocks from what 

 were then granite islands should have been anywhere left upon the 

 sea-bottom around them is improbable ; that no block from the 

 central tors should have travelled down the ordinary channels of 

 denudation in later times is also contrary to our usual experience in 

 such cases. Therefore we have no right to assume the existence of 

 glacial conditions to explain the occurrence here and there of a 

 block of granite or other rock of Devonshire origin over the area 

 surrounding those rocks in place. 



If the red granite cannot have been derived from Dartmoor, 

 where there are some beds of that colour, or beds which would 

 probably in similar circumstances become of that deeper colour on 



