120 PROCEEDINGS OE THE GEOLOGICAX SOCIETY. [Jan. 8, 



lie with a dip gradually diminishing in amount till it does not 

 exceed 4°*. 



The section just described in detail may be regarded as typical ; 

 and the relations exhibited by the Jurassic strata here are found 

 to characterize them wherever they appear in the north-east of 

 Scotland. They almost everywhere offer evidence of considerable 

 disturbance and faulting. At the points furthest removed from their 

 contact with the Palaeozoic rocks, tbis disturbance is at its minimum ; 

 but as we approach these latter, tbe angle of dip is found to 

 increase, the folds become shorter and sharper, and the dislocations 

 more numerous, while at the actual junction of the two series of 

 strata the younger ones are often crumpled and crushed in the 

 most remarkable manner. 



§ 2. Relations of the Strata North of the typical line of Section. 



Silurian strata with characters similar to those already described, 

 and containing veins of white quartz, red granite, &c, are 

 found rising to a height of from 500 to 600 feet between the 

 burns of Clyne Kirk and Kintradwell, in the latter of which they 

 are again seen traversed by veins of quartz and felspar, the latter 

 sometimes decomposed into kaolin. I am indebted to Captain 

 Houston, of Kintradwell, for guiding me to these sections. At the 

 openings of the ravines of Achrimsdale, Clyne-Milltown, and the 

 small nameless burn just north of Kintradwell there are exposures 

 of the Jurassic strata ; but the contact of these with the Silurian 

 strata is not seen. The interesting section of Allt-Chollie (Coly- 

 burn) has been already described ; and in Allt-na-cuil and some 

 smaller ravines to the north, though the actual junction is not ex- 

 posed, the Jurassic strata are evidently greatly disturbed near their 

 contact with the Silurian. 



Near the Lothbeg river and from that point northwards the 

 Silurian gneiss passes into or is replaced by the beautiful red, often 

 porphyritic granite, which covers a considerable area on the confines 

 of Sutherland and Caithness, and forms the great mass of the Ord. 

 Along this portion of the coast the Jurassic strata are in contact with 

 the granite or with the thin strip of Middle Old Red Sandstone 

 (Caithness flags) Avhich flanks it for a distance of five miles, and which 

 will be more particularly noticed hereafter. Between Lothbeg and 

 Helmsdale the strip of Oolitic rock, which is from a quarter of a mile 

 to half a mile wide, is cut through by a number of brooks : and in 

 some of these, especially in Allt Cuil-nan-Gabhar (Culgour Burn), 

 Wester Gartie Burn, Midgartie Burn, andAllt-gharashtiemore (Gartj-- 

 more Burn), the rocks, as they approach the line of their junction 

 with the Old Bed strata, are seen to be more and more disturbed. 

 About Helmsdale the • coast is formed by the granite, the Jurassic 

 strata having been wholly denuded away ; and north of that town 

 the latter form only a very narrow strip, which is cut through in 

 many places by small inlets of the sea and deep ravines. Some- 



* See also Murcbison in Trans. Geol. Soc. 2nd ser. vol. ii. part 3. p. 55. 



