Messrs Feacli and Home on the Glaciation of Caithness. 351 



by ourselves. The only record of stratified beds underneath 

 the boulder clay rests on the authority of Mr Dick.* He 

 describes a section seen in a small stream running into Gill's 

 Bay, which has cut a channel down to the solid rock through 

 a deposit of grey boulder clay, containing chalk, chalk-flints, 

 and oolitic rocks, and yielding remains of Mactra, Cyprina, 

 T%irritella, and Dentalium. Below the boulder clay he 

 observed a bed of gravel with broken shells resting on red 

 sandstone. Again, on the south side of the Moray Firth, 

 one of us found, in the summer of 1880, while prosecuting the 

 geological survey of Banffshire, a series of stratified sands, with 

 marine shells, which are covered in part, with boulder clay. 

 These shelly sands indicate a marine depression to the extent 

 of 500 feet in inter-glacial times. It would seem, then, that 

 there is evidence in favour of the existence of stratified beds 

 with Arctic shells below the boulder clay in the north of 

 Scotland. But even admitting the existence of such deposits, 

 it is difficult to see how floating ice could so act on them as 

 to produce the phenomena presented by the shelly drift. In 

 such a case there would have been signs of stratification in 

 the deeper sections, as, for instance, in the Scrabster Harbour, 

 where the deposit is upwards of 100 feet thick, ^^ay, more, 

 such a theory does not account for the greater abundance of 

 marine shells along the eastern seaboard, and the gradual 

 increase of blocks derived from the Caithness flagstones as 

 we move inland from the east coast. Neither does it explain 

 the deflection of the local ice. 



It is perfectly evident, therefore, that the phenomena of 

 the grey shelly boulder clay cannot be satisfactorily explained 

 on the hypothesis of floating ice, and we are therefore forced 

 to accept the only remaining solution, that it is really a 

 product of land ice. Indeed, when we view the evidence 

 supplied by the striated surfaces and the boulder clay in the 

 light of our previous work in Orkney and Shetland, it will 

 readily be admitted that the glacial phenomena of these 

 widely separated areas have a close relation to each other. 

 They point to the union of the Scotch and Scandinavian ice- 

 sheets on the floor of the North Sea. The ice which flowed 

 * Life of Robert Dick, by Smiles, p. 228. 



