4d On the Coal-field of Sutherland. 



of recurrence and of dimensions which I noticed at the begitining 

 of this part of the subject. 



The sandstone is sometimes of a pure white, but rarely very 

 solid ; much oftener it is extremely friable. Occasionally it 

 contains fragments of the same kind of sandstone, or presents, 

 what is not very common, a simple white sandstone conglo- 

 merate. In one or two places, I remarked that it was inter- 

 sected in every direction by laminar veins of great tenuity, 

 reticulating in an intricate manner, and of a whiter colour than 

 the body of the rock. They are also harder; since, on the 

 exposed surfaces, they protrude in the manner so often seeu 

 in granite, where similar veins exist. I should also here ob- 

 serve, that among these sandstone beds, there occur conglo- 

 merates with a sandstone base, containing fragments of shale 

 <5r of limestone, or of both. The variety of appearance which 

 they hence present is considerable, but requires no further 

 description. The shales are of various colours and of different 

 degrees of solidity or tenacity. Bluish-black, black, and paler 

 grey, are among the most common; but red, yellow, and 

 purple are not unfrequent. That which is requisite to be said 

 respecting the coal, will better find its place in the historical 

 account of the workings at Broras. 



Such is the variety bf substances, and the general order of 

 succession in this coal-field, as far as it can be ascertained, 

 and as far indeed as it seems either necessary or useful that it 

 should be known. 



• For those who are desirous of seeing more particularly the 

 minute arrangements occurring in the upper part of the series, 

 I shall content myself with referring to the working section of 

 the Brora coal. I shall, in terminating this part of the 

 subject, content myself with summing up, in the most 

 general manner, the order of succession in the inferior parts, 

 as far as that could be deduced with any probability. Arid, 

 to render it more useful, I shall exhibit it as it occurs in 

 difi*erent places. 



Granite. 



Coarse conglomerate of various rocks. 



Calcareous conglomerate of various rocks in a calcareous base. 



Grey compact, and granular limestone. 



