350 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



It is necessary to add that I could detect no indications of the primary 

 schistose rocks passing into the Old Red Sandstone, as mentioned 

 by Mr.Prestwich (pp. 141 and 145) ; and that the micaceous schists at 

 the village of Gamrie, coloured in his sections as the primary rocks, 

 present an appearance not uncommon in various parts of the Old 

 Red Sandstone, to which formation I have no doubt they belong. 

 The gradual passage of the primary schistose rocks into Old Red 

 Sandstone is so completely at variance with every observation I have 

 had the opportunity of making in tliis part of Scotland, that I was 

 glad to find the phenomena exhibited at the junction of these rocks 

 near Troup Head, and in the neighbouring parts of Aberdeenshire, 

 the same as I had been accustomed to witness, modified only by the 

 occasional occurrence of grauwacke and trap-rocks*. 



Appendix. 



During October 1839, I visited the Orkney Islands, and have 

 found Mr. Clouston's statement given above (p. 348) to be correct. 

 The great conglomerate near Stromness rests on gneiss, which is 

 traversed by veins of granite and of compact felspar, resembling 

 those of Morayshire, and on a granite containing much red felspar. 

 In the Island of Gremsey, between Pomona and Hoy, the granite 

 appears to have been protruded in a solid form through the con- 

 glomerate, which contains beautiful crystals of quartz, galena, and 

 heavy-spar. The bituminous flags with fish rest directly on the 

 conglomerate. At Shandwick, in Pomona, I collected many speci- 

 mens of the plants found at Lethen and Gamrie, which were 

 associated with fish of the same species as at those places. The 

 partings of these flags are sometimes coated with a pure bitumen 

 entangled in calc-spar ; and a mixture of galena and blende (as ascer- 

 tained both by external characters and chemical examination) was 



* Near the village of Aberdour, in Aberdeenshire, ten miles E. of Gamrie, the 

 finer-grained red sandstones repose unconformably on the older rocks, without 

 the intervention of the inferior conglomerates ; and a little below the Manse, on 

 the estate of Auchmedden, a fault occurs, which has brought shale-strata, con- 

 taining nodules hke those of Gamrie, into contact with the sandstones, — the strata 

 on each side dipping at different angles, as represented in PI. XI. fig. 11. In the 

 few nodules which Mr. C. Smith and myself could procure, there were no fish ; 

 but I have no doubt that they would have been found had we had the means of 

 digging. Between this and Troup Head the inferior sandstones and conglo- 

 merates are developed on the most magnificent scale, and form cliffs more than 

 600 feet in perpendicular height, against which the ocean constantly dashes ; 

 and it would rapidly waste them away, were they not protected by great masses 

 of trap, and the hardness and position of some of the sandstone strata. Nowhere 

 is more magnificent sea-scenery to be witnessed than along these stupendous 

 cliffs, the careful examination of which would reward the geologist. 



In October last, the Eev. Mr. Gordon, of Birnie, discovered, near Rhynie on 

 the Bogie River, ten miles south of Huntly, in Aberdeenshire, in that great 

 outlier of the Old Red Sandstone extending to Kildrumie Castle, and laid down 

 in great detail in Dr. M'Culloch's map, thick beds of shale, with nodules similar 

 to those of Lethen, &c., and containing remains of fish. This shale rests on a 

 disintegrated yellowish sandstone, and is covered by a great thickness of yellow 

 and red soft sandstones and conglomerates, like those of Cromarty and Tynat, 

 on which thick beds of a hard pink sandstone rest. — Feb. 1, 1840. 



