304 ]M r. MuRciiisoN on the Coal-field of Brora in Sutherlandshire, 



PI. VIII.*) These are overlaid by an indurated white quartzose sandstone, 

 which runs out into a long- sc«r from the south bank of the river Brora. The 

 stratification of the coast reefs at Ardasie Point on the north bank of the river 

 is indistinct, and there appears to have been a great subsidence from thence, 

 by which the highest beds of the district have been depressed below the level 

 of the sea : hence no rocks are to be seen throughout the sandy bay north- 

 east of the river Brora, the low grounds between it and Clynemilltown being- 

 covered with blown sand and gravel. 



At Kintradvvell are the first appearances of beds differing from any pre- 

 viously mentioned : some of these resemble the cornbrash limestone, and 

 others the forest marble ; the prevailing fossils being the avicula inequivalvis 

 and the terebratula inconstans. One of these beds of shelly limestone is 

 overlaid by shale in a low hillock on the shore, and below it are reefs of 

 bluish calciferous grits containing a few fossils, among which the nerifa laevi- 

 gata was observed. These grits are traversed by a vein two feet and a half wide, 

 in texture resembling- quartz-rock and having a conchoidal fracture : the tilting 

 of the strata in opposite directions at this point indicates some powerful dis- 

 turbing cause. After a short interval of low shore, the sandstone and shale 

 above the beds of shelly limestone form cliffs, near Colyburn, higher than 

 those of any other part of the Brora coast. Here the granitic rock advances 

 from the mountain range, occupying both sides of a precipitous ravine ; and 

 the secondary strata near it are much dislocated : the sandstone is in some 

 places indurated, and accompanied by brown haematite ; and porcelain clay 

 (Kaolin) is dug- in the cliff, probably derived from the decomposition of felspar. 

 This advance of the mountain range forms a natural division between the vales 

 of Brora and Loth. 



Loth. 



This vale is about six miles in length from S.W. to N. E., and varies in 

 breadth from half a mile to one mile and a half. It is trough-shaped : the 

 strata, which are highly inclined against the mountains of the interior, sink in 

 the centre of the vale, and again rise on the exterior into low hills towards 

 tlie sea. This coastward rise of the beds is apparently owing to the prox- 

 imity of the granitic rock, which is here and there seen through the accumu- 

 lations of blown sand. In the lowest or central part of the valley, black shale 



* I have the authority of Mr. Miller, who has examined my specimens, for statins: that the 

 variety of B. sulcatus from these shales at Brora is identical with the belemnite of the 0.\ford 

 clay. 



