J9 Pn the Coal-field of Sutherland^, 



mor6 limited extent and less satisfactorily, by following thew 

 elevated edges along the sea line, where the investing covering 

 of earth has been removed. As the ebb is here considerable, 

 the geologist will find his investigations much facilitated by 

 choosing the time of low water for his operations. 



The mass of granite described in the first part of this paper 

 divides the sandstone of Caithness from this deposit; but 

 while, on that side, the conglomerate strata occur in small 

 quantity and are fine grained, often much resembling granite, 

 and commonly composed of a very limited number of ingre- 

 dients, no indication was observed of that well-known variety 

 of conglomerate which is composed of many primary rockss, 

 and in which the fragments are of various and generally of 

 large dimensions. 



But on that side of the granite where this coal-field lies, the 

 first substance found reposing on it is a conglomerate of a 

 coarse texture, formed of many different rocks ; these being 

 loosely agglutinated by gravel and sand of the same materials. 

 The fragments are often so large as to reach to many hundred 

 pounds in weight. The substances of which they consist are 

 chiefly gneiss, granite, micaceous schist, argillaceous schist, 

 and sandstone. 



Where this conglomerate first appears, it forms an insulated 

 liigh rock, now unconnected with the granite ; but lower por- 

 tions of it skirt the cliffs of that rock for a certain space along 

 this part of the shore. Its extent, however, is not considerable; 

 while, in many places, it forms a very thin bed. Tracing it 

 along the granite, it at length disappears either partially or 

 entirely, and in many parts of the coal-field it is altogether 

 absent ; so that the next strata in the order of succession come 

 into contact with the fundamental granite of the mountains. 

 I did not succeed in finding, in the northern part of this deposit, 

 any of the ordinary red sandstone to which it must be sup- 

 posed to belong, or any rocks resembling those which occur on 

 the northern side of the granite ; but to the southward there 

 is found interposed between it and the granite, that series of 

 red sandstone which extends into the southern parts of Sutherr 

 land and into Cromarty. It may be concluded that the conglo- 

 merate lying near the granite, on the northern part of the coal- 

 field, is partial and evanescent, and that the secondary strata^ 



