in Sutherland, Ross and the Hebrides. 357 



district I may here state, that the subdivisions, which we hope to establish, 

 induce me to assign that portion of it which flanks the Brora coal-field to 

 the old red sandstone. 



Oolitic Series. 

 Denudation of Braambury and Hare hills. 



The limestone and sandstone of these hills constituting the highest beds of 

 the Brora district, have, by means of their abundance of characteristic fossils, 

 been identified with the calcareous grit beneath the coral rag. I remarked 

 in my former paper, that these hills probably owe their present form to denu- 

 dation ; which supposition is now confirmed by the exposure on their surface 

 of innumerable parallel small furrows and irregular scratches, both deep and 

 shallow, — such, in short, as can scarcely have been produced by any other ope- 

 ration than the rush of rock-fragments transported by some powerful current. 

 Upon my first visit, these markings being only imperfectly visible in one 

 situation near the quarries, I was unwilling to enlarge upon the fact ; but 

 Mr. Barton, the director of these works, has since cleared away the turf from 

 other parts of the surface, and these operations have uniformly exposed si- 

 milar phsenomena. These hills have been swept free of all gravel, except on 

 the N. and S. of E., towards which points the beds are prolonged into the 

 plain of Clyne Milltown, where there is a thick accumulation of boulders of the 

 old red conglomerate mixed up with the softer detritus of the denuded hills. 

 The furrows and scratches appear to have been made by stones of all sizes, 

 which (with the occasional exception of lines slightly diverging, probably 

 occasioned by the smaller pebbles coming forcibly in contact with the larger,) 

 preserve a general parallelism with a direction from N. W. to S.E.* By a pro- 

 longation of these lines into the interior, the boulders of red conglomerate may 

 be traced from the plain of Clyne Mifltown to the mountain range which is 

 composed of that rock, and particularly to the precipitous escarpments on the 

 south of Loch Brora. Although the dip varies much on the different sides and 

 summit of the denuded hills, being about 20° north on their north-western 

 flank, and only 10° E. near the quarries ; still in all such situations the furrows 

 and scratches preserve an uniform direction from N.W. to S.E. ; thus indica- 

 ting the great force of a current, unaltered in its course by any inequalities of 

 the surface over which it rolled. These appearances so closely resemble those 

 in other places described by Sir James Hall and Dr. Buckland, that further 

 detail seems unnecessary ; and the large slabs which I have had the pleasure 

 of presenting to the Society, completely elucidate the case. 



* By compass. 



