the Primary Rocks and the Oolitic Series in the N'orth of Scotland. 131 



a brownish grey, thin-bedded sandstone, which appears on the whole to con- 

 form to the dip of the conglomerate. Two masses of granite interrupt the 

 regular range of the sandstone strata, which are in consequence tilted in op- 

 posite directions from these granitic nuclei. 



The upper beds of the same sandstone rise high in the hills between Strathy Kirk and Bighouse 

 Bay ; and although these hills are much obscured by vast masses of alluvium, a good section is 

 seen on the side of the high road near the summit of the hill, where the sandstone, being very fine- 

 grained, is extensively quarried. Here also are observed thin, flaggy, calcareous beds, sometimes 

 separated from each other by black laminae, apparently of carbonaceous matter, and overlaid by 

 a compact, lamellar limestone, which is burnt for use, and forms a most powerful cement. The 

 dip of these beds is N.N.E. and their inclination varies from horizontal to an angle of 7° or 8°. 



After a short interruption, the cliff recommences on the eastern side of Bighouse Bay, and rises 

 to a considerable height. Its lowest beds are analogous to the highest part of the Port Skerry 

 section ; and over them is a succession of thick deposits nearly in the following ascending order. 



Dip E.N.E. 25°. 



1. Bluish, calciferous, gritty, thick beds, with reddish exterior. 



2. Greenish, flaggy sandstone, alternating with calcareous beds. 



3. Brown sandstone of great thickness, fifty to sixty feet, but very finely laminated. 



4. Shaly beds, with some calcareous matter. 



5. Whitish sandstone. 



6. Lamellar, smoke-grey limestone, same as described on the hill above Strathy Kirk ; and 

 here also burnt for use. 



7. Thin-bedded, flaggy sandstone. 



8. Summit — alluvial detritus of considerable thickness. 



The only organic remains we discovered in this series, were the scales of fish, irregularly dis- 

 tributed between the lamina; of some of the more calcareous and slaty beds. 



In proceeding eastwards from Bighouse to Sandside, the cliffs, increasing in altitude, become 

 more fissile and slaty towards their summits; and, for the first time, are perceived those, deep and 

 long transverse ravines so peculiar to the coast of Caithness, perhaps originally produced by dis- 

 turbing forces which cracked and split up the fissile beds, and which, in many instances, have been 

 subsequently modified by the encroachments of the sea. Many of these clefts look like great 

 empty metalliferous veins, and afford excellent detailed sections of the strata* : in one of them we 



observed the order to be as follows, beginning with the lowest bed. 



Feet. 



1. Thin-bedded calcareous shale and impure limestone, with four strong) .„ 



bands of calcareous sandstone J 



2. Brownish grey sandstone 20 



3. Coarse, calcareous sandstone 7 



4. Thicker sandstone ^5 



5. Transported and broken materials ^ i 



The effect of abrasion in these cliffs is shown in numerous detached pin- 

 nacles and turrets standing out in the sea, some of which are still connected 

 with the main land by ridges of the sandstone and calcareous shale. Imme- 



* See Plate XIV. fig. 1. 



s2 



