The Scottish Naturalist. 247 



west, until the ice flow issuing from the high grounds of Kirk- 

 cudbright at last succeeded in reaching the middle of the Irish 

 Sea basin. This gradual modification of the general ice-flow in 

 that basin would of course give rise to a redistribution of the 

 ground -moraine, and the Irish erratics would then travel on- 

 wards underneath the Scottish ice, and eventually reach the low 

 grounds of Lancashire and Cheshire, along with erratics from 

 Criffel and the Cumbrian mountains. It is, therefore, quite 

 unnecessary to suppose that the mer de glace of the North 

 Channel actually crossed the whole breadth of the basin of the 

 Irish Sea to invade Lancashire, Cheshire, and North Wales. 

 Had this been the case, chalk flints, chalk, and many other 

 kinds of rock derived from the north of Ireland, and even from 

 Arran and Argyle, would have abounded in the drifts of the 

 west of England. Erratics coming from Ireland could not 

 possibly have travelled underneath Irish ice further east than 

 the Isle of Man. There or thereabouts, as I have said, the 

 mer de glace of the North Channel would begin to encounter 

 the ice streaming down from the uplands of Galloway and the 

 mountains of Cumberland ; and as the ice from these quarters 

 increased in thickness, it would gradually override what had 

 formerly been the bottom-moraine or till of the North Channel 

 mer de glace. Thus Irish erratics would become commingled 

 with erratics from Criffel, &x., and be rolled forward in a 

 southerly and south-easterly direction. The chalk-flints in the 

 drifts of Lancashire, Cheshire, &c, are therefore merely 

 remanies — the relics of the bottom - moraine of the North 

 Channel mer de glace rearranged and redistributed. And this 

 is why they and other Irish rocks are so comparatively rare 

 in the glacial accumulations of the west of England. 



Thus all the instances of " intercrossings " adduced by Mr 

 Mackintosh, as favouring the iceberg theory, and condemning 

 its rival, I would cite as proving exactly the converse. So far 

 from presenting any real difficulty to an upholder of the land-ice 

 theory, they, in point of fact, as I have already remarked, lend 

 that view additional support. 



It is not my purpose to criticise all the arguments and reasons 

 advanced by Mr Mackintosh in favour of his special views, but 

 I may be allowed a few remarks on the somewhat extraordinary 

 character of the agents which, according to him, were mainly 

 instrumental in producing the drift -phenomena of Western 

 England. Before doing so, however, I may point out that, in 



