316 Proceedings of the Royal Physical Society. 



XVI. The Glaciation of Caithness. By B. K Peach, Esq., 

 F.E.S.E., F.G.S., and John Horne, Esq., F.RS.E., 

 F.G.S. [Of the Geological Survey of Scotland.] 



(Read 20tli April 1881.) 



I. Inteoduction. 



In the course of our annual leave of absence from official 

 work, we visited Caithness in the autumn of 1880, for the 

 purpose of continuing our investigations regarding the exten- 

 sion of the ice in the North Sea in the Glacial period. The 

 results of our previous observations in Shetland and Orkney, 

 which have appeared in the Quarterly Journal of the Geologi- 

 cal Society,^ point to the conclusion that during the climax of 

 the Ice Age the Scandinavian and Scotch ice-sheets coalesced 

 on the floor of the North Sea, and that a great portion of 

 this ice-field moved in a north-west direction towards the 

 Atlantic. We showed that a careful examination of the 

 rochcs moutonnees, the striated surfaces, and more especially 

 the dispersal of the stones in the boulder clay, compelled us 

 to admit an ice movement from the North Sea to the 

 Atlantic during the primary glaciation. We inferred that 

 the Shetland group must have been overridden by the Scan- 

 dinavian portion of the ice-field, as the striated surfaces 

 clearly point in that direction ; while the presence of Scotch 

 rocks in the Orcadian boulder clay led us to the conclusion 

 that these islands must have been overflowed by the Scotch 

 ice-sheet. Further, we adduced evidence to prove the 

 existence of local glaciers in Orkney and Shetland long after 

 the great mer de glace had melted back from the old coast 

 lines of these northern islands. 



The glacial phenomena of Caithness have an important 

 bearing on the general question of the extension of the ice in 

 the North Sea, and although they have been described by 

 many writers, we resolved to visit the county with the object 

 of gathering evidence regarding the direction of the ice-flow 

 and the probable physical conditions which prevailed during 

 the accumulation of the superficial deposits. In the sequel 



* Quart. Jour. Geol, Soc, vol. xxxv., p. 778; xxxvi., p. 648. 



