Messrs Peach and Home on the Glaciation of Caithness. 337 



Oolite formation, septarian nodules, along with chalk and 

 chalk-flints. Indeed, over all the tract occupied by the shelly 

 drift chalk-flints are occasionally met with on the surface, 

 having escaped denudation while the matrix which enclosed 

 them has been worn away. Some pieces of jet were also 

 obtained by Mr C. W. Peach in the sections at Wick, and 

 several specimens of belemnites were found by him both at 

 Wick and in the Thurso river. It ought to be borne in mind 

 that the secondary rocks in the dark-grey clay are co-exten- 

 sive with the shells, and where these blocks occur shells are 

 common. These foreign blocks are hardly ever found in 

 those places where the deposit is only a foot or two thick, 

 and the same remark applies to the organic remains. In 

 that case the blocks are almost invariably composed of the 

 underlying rocks. 



We believe that Mr C. W. Peach was the first to recognise 

 the close resemblance between the blocks of the secondary 

 rocks in the shelly boulder clay and their representatives on the 

 Sutherland shire coast. Many of the included blocks contain 

 the same fossils as those chronicled from the latter locality. 

 Indeed, nearly all the blocks of secondary rocks, save the 

 chalk and chalk-flints, might quite well have been derived from 

 the Sutherlandshire coast, or the outliers which occur in the 

 basin of the Moray Firth. But though cretaceous rocks do 

 not occur in place on the shores of the basin now referred 

 to, they are believed to exist on the bed of the Firth. In 

 addition to these, several blocks of fossil wood are met with 

 in the shelly drift which are identical with those found by 

 us in the Odin Bay section, in Stronsa, Orkney. Sections of 

 this rock show distinct cell structure under the microscope, 

 and they have been determined by Mr Kidston of this 

 Society as specimens of Feuce Lindlc7ja7ia of Oolitic age. The 

 same rock is embedded in the ooHtic shales in Sutherland- 

 shire, where it is burned for lime. 



The occurrence in the shelly boulder clay of these blocks 

 of secondary rocks wliich are known to exist in the basin of 

 the Moray Firth, is an additional argument in favour of the 

 theory that the ice-flow across the Caithness plain was 

 towards the north-west. 



VOL. VI. Y 



