Some remarkable Boulders in the Isle of Man, 219 



January (1891) meeting. Meantime, I sent another speci- 

 men to Mr. J. G. Goodchild, of Edinburgh, and received from 

 his colleague, Mr. A. Macconochie, a letter in which he 

 expressed the opinion that the boulder resembled a rock 

 found in Ailsa Craig, an opinion with which Mr. B. N. Peach 

 concurred. 



By a singular coincidence, Mr. J. J. H. Teall, of H.M. 

 Geological Survey, described the Ailsa Craig rock at the 

 same meeting as that at which Professor Cole's note was 

 read. Mr. Teall points out four several particulars in which 

 my rock resembles that of Ailsa Craig, and differs from the 

 Mynydd Mawr examples. 



In view of the concensus of opinion in favour of the 

 fdentification of the rock with the Scottish granite and 

 against its allocation to North Wales, I cannot resist the 

 conclusion that boulders from Ailsa Craig were actually 

 carried to the Isle of Man and North Wales during the 

 Glacial Epoch. This is the first example of the occurrence 

 of rocks from the Clyde Basin as erratics in the basin of the 

 Irish Sea. 



The discovery throws a remarkable light upon the 

 speculations of those able investigators, Mr. John Home 

 and Professor James Geikie. 



Mr. J. Home long ago* showed that the Isle of Man had 

 been glaciated by a great sheet of ice coming down from 

 the mountains of Galloway, and aided by contingents from 

 the Lake District and Ireland. He pointed out that a 

 deep submarine rock-channel existed round the N.E. coast 

 of Ireland, from Rathlin Island down to about the latitude 

 of Dublin, and he suggested that this might be a "deflection 

 basin" cut out by ice which came down the Firth of Clyde, 

 was cleft by the Antrim coast line, and flowed, one element 

 westward into the Atlantic, and the other southward, 

 through the North Channel into the Irish Sea. 



* Tratis, Geol, Soc. Edin, Vol. ii., part 3. 



