The Scottish Naturalist. 251 



from the watershed of the Galloway mountains, to the north of 

 which the strne, rocJics moutonnees, and track followed by erratics, 

 indicate an ice-flow towards the north-west, north, and north- 

 east. It is therefore absolutely certain that at the time the 

 granite erratics are supposed to have sailed away from Criffel 

 on floating ice, the whole of the southern uplands of Scotland 

 were covered with a great ice-field extending from Wigtown to 

 Berwickshire; so that, according to Mr Mackintosh's hypothesis, 

 we should be forced to believe that an ocean-current originated 

 in Criffel itself! But waiving this and other insuperable objec- 

 tions which will occur to any geologist who is familiar with the 

 glacial phenomena of the south of Scotland, and confining 

 myself to the evidence supplied by the English drifts, I would 

 remark that Mr Mackintosh's hypothesis is not consistent with 

 itself. A current flowing in the direction supposed could not 

 possibly have permitted floating ice to sail from Cumbria to the 

 Isle of Man, to Moel-y-Tryfane and Colwyn Bay. Mr Mac- 

 kintosh admits this himself, but infers that the transport of the 

 Cumbrian erratics may have taken place at a different time. 

 But how could this be, seeing that the Criffel and Cumbrian 

 erratics occur side by side in one and the same deposit? 

 Again, the hypothesis of an ocean -current coming from 

 Criffel is inconsistent with the presence of the Irish chalk-flints 

 in the drifts of the west of England. Did these also come at 

 a different time? And what about the dispersion of erratics 

 from Great Arenig, which have gone north-east and north-north- 

 east, almost exactly in the face of the supposed Criffel current ? 

 Here an ocean-current is obviously out of the question ; and 

 accordingly we are told that this dispersion of Welsh boulders 

 was probably the result of wind. But why should this wind 

 have propelled the floating ice so far and no farther in an 

 easterly direction? Surely if floating ice was swept outwards 

 from Great Arenig as far as Eryrys, bergs must have been 

 carried now and again much farther to the east. And if they 

 did not sail eastwards, what became of them? Did they all 

 melt away immediately when they came into the ice -laden 

 current that flowed towards the south-east ? * A still greater 



1 Mr Mackintosh says nothing about the "carry" or direction of the 

 erratics in West and South Wales. Were the paths of these erratics de- 

 lineated upon a map, we should find it necessary to suppose that the wind or 

 sea-current by which the floating ice was propelled had flowed outwards in 

 all directions from the dominant heights ! 



