Messrs Peach and Home on the Glaciation of Caithness. 317 



we hope to show that in many respects there is a close 

 resemblance between the glacial phenomena of Orkney and 

 tliose of the Caithness plain. We obtained evidence which 

 shows that the local ice, shed from the hilly ..ground along 

 the county boundary, moved E., KE., and N. till it debouched 

 on the plain, where it was compelled to veer round to the 

 north-west in harmony with the general movement in the 

 low ground of the county. 



II. Previous Literature on the Subject. 



The boulder clay of Caithness has long been celebrated for 

 the abundance of organic remains which are present in that 

 deposit, and its origin has consequently given rise to con- 

 siderable discussion. The occurrence of marine shells in the 

 boulder clay was first made known by Hugh Miller in the 

 pages of The Witness in 1847, where he states that Mr John 

 Cleghorn of Wick and Mr Dick of Thurso had supplied him 

 with shells from their respective sides of the county.* The 

 writer of the article also states that, to Mr Dick's chagrin, he 

 had come across an old work, entitled, " Minutes of Observa- 

 tions Drawn Up in the Course of a Mineralogical Survey of 

 the County of Caithness in 1802 by John Busby, Edinburgli," 

 wherein were chronicled several instances of the occurrence 

 of marine shells in the blue clay of Caithness. The survey 

 was made at the instance of Sir John Sinclair. 



In his rambles across the county Mr Dick brought to light 

 many localities where this deposit yields marine shells, and 

 blocks of fossiliferous secondary rocks along with chalk flints. 

 He detected the ice-markings on the rocks at Thurso, and he 

 noted the occurrence of erratics at various points which had 

 travelled far from their parent sources.-f* Indeed, his long- 

 continued examinations of the sections from the Thurso river 

 to Freswick burn and southwards to Dunbeath, led him to the 

 belief that the boulder clay, in some way or other, was of 

 glacial origin. 



* "Rambles of a Geologist; or, Ten Thousand Miles over the Fossili- 

 ferous Deposits of Scotland. " 



t See "Life of Robert Dick," by Smiles, pp. 159, 164, 169, 184, 187, 195, 

 223, etc. 



