354 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Dec. 1, 



Contents {continued). 



Crystalline Rocks of the Shetland Isles. 

 Old Eed Sandstone of the North-East 

 of Scotland. 



Lower Old Red. 



Caithness Flags,or Middle Division 

 of the Old Red Sandstone of the 

 N.E. of Scotland and the Ork- 

 ney Islands. 



Animal and Vegetable Remains of 



the Caithness Flags. 

 Upper Old Red of Caithness. 

 Old Red of the Orkney Islands. 

 Old Red of the Shetland Isles. 

 Greneral View of the Old Red or De- 

 vonian Rocks. 

 Lias and Oolite in the North of Scotland. 



iNTRODTJCTioisr. — In this memoir I propose to give a general sketch 

 of the succession of the stratified rock-masses which occupy the 

 northernmost counties of Scotland, or those of Sutherland, Caithness, 

 and Ross, followed by brief notices on the Orkney and Shetland Isles, 

 as determined by former and recent observations. 



Having commenced to labour in this region in 1826, 1 then simply 

 gave, as a first result, the account of the Oolitic coal-field of Brora, 

 and of the Lias and Oolites of both the east and west coasts, in- 

 cluding the Hebrides, with brief allusions to the bituminous schists 

 of Caithness containing fossil fishes *. For, although I even then 

 had traversed portions of the crystalline rocks, I considered all such 

 masses as out of the sphere of my observation, presuming that their 

 mineral and other characters had been adequately made known by 

 Macculloch and others who were looked upon as authorities. In 

 short, it was deemed a sufficient effort for a young geologist, as I 

 then was, to point out the relative position of certain members of 

 the Secondary series, to collect their organic remains, and to show 

 the relations of such strata to their equivalents in England. 



In the following year Professor Sedgwick and myself, devoting 

 our efforts to the examination of the structure of the Northern 

 Highlands, produced a memoir in which, after a brief allusion to 

 the older and crystalline rocks, we gave the first account of the true 

 order of the Old Eed Sandstone and superposed masses, which we then 

 showed to consist of three parts, viz. Lower Sandstone and Conglo- 

 merates, Central Caithness Flagstone, and overlying Red Sandstones 

 of Dunnet Head and the Orkney Islands f. In that same summer we 

 also traced the position of the so-caUed primary limestones of Assynt 

 and Durness, and ascertained that these were intercalated in great 

 bands of quartz -rocks and surmounted by chloritic, micaceous, and 

 even gneissose strata. "We further affirmed that those crystalline 

 masses, together with the granite and other igneous rocks which 

 traversed them, had afforded the materials out of which the conglo- 

 merates and sandstones at the base of the Old Red Sandstone of the 

 East Coast were formed. Thus far our original views have proved to 

 be true. Owing, however, to stormy and wet weather which we en- 

 countered on the west coast of Sutherland, and our limited time, we 

 were precluded from observing the true relation of certain vast masses 

 of red conglomerate, which, occupying lofty mountains, have recently 

 been shown to underlie the quartzose and crystalline limestones just 



* Trans. Geol. Soc. 2nd ser. vol. ii. p. 313. 



t I had visited the Orkneys during the previous year. 



