36 Reports and Proceedings. 



The Boulder-till occurs at G-ilmoreliill of great thickness, the 

 valley of the Kelvin having been scooped out of it down to its 

 present bed, it is of the same normal character as that which covers 

 the country around Glasgow. It contains many striated stones 

 belonging to various rock-formations. The direction of the striae on 

 the surface of the underlying rocks at the quarry shows that the 

 great ice-sheet had passed over this part of the district nearly from 

 west to east, which is the average direction of the glacial strige in 

 this tract of Scotland. 



2 "On the Claystones of Arran." By the Eev. John F. Potts, 

 B.A. — The author of this paper stated that by the familiar term 

 claystone he desired to indicate the whole group of the Arran rocks, 

 of which the base was a felspathic paste. These rocks are beauti- 

 fully developed in the pretty Ben Leister Glen, at the N.W. corner 

 of Lamlash Bay, where there exist upwards of a dozen large dykes 

 of the several varieties. Singular to say, these elaystone dykes are, 

 with one exception, always found in that Glen associated with 

 parallel and contiguous dykes of common basalt or greenstone. The 

 former are, however, invariably many times as thick as the latter, 

 and were evidently injected first into the fissures. The igneous 

 origin of claystone was the point first demonstrated, although at- 

 tention was called to some extraordinary appearances in the Glen, 

 which taken alone would lead to an opposite inference, such as the 

 existence of pebbles in the heart of the claystone, and the curious 

 fact, already alluded to, of double dykes occurring together with 

 such frequency. But this latter phenomenon was explained on the 

 supposition of two distinct sets of volcanic disturbances. Claystone, 

 being a less crystalline rock, must have been erupted near the place 

 where it is now found. The Holy Isle, Dun Dhu on the CorrygUls 

 shore, and the well-known Windmill Hill near Brodick are all huge 

 pyramids of claystone resting upon the same sandstone that is found 

 in the Ben Leister Glen containing the dykes. These three re- 

 markable hills were probably ancient volcanoes, and as they are all 

 equally near the glen in question, the terribly shattered character of 

 its bottom may be explained. A subsequent renewal of volcanic 

 action opened still further the fissures formerly produced there, and 

 these, becoming filled with a more fluid lava, caused the phenomenon 

 of the double-dykes. The author desired it to be understood that he 

 made these suggestions merely with the hope of attracting attention 

 to this very interesting group of the rocks of Arran. 



II.— 3rd December, 1868. Edward Hull, Esq., F.R.S., Vice- 

 President, in the chair. 



The Chairman exhibited a specimen of native copper in trap, and 

 Prehnite embedded in analcime. 



Mr. John Young exhibited a fossil fruit nearly allied to Trigono- 

 carpum, from the Carboniferous limestone shales of Calderside, High 

 Blantyre, but it differs from that genus in possessing eight ribs near 

 the apex. Also from the same beds, Griffithides mesotuberculatus, 

 M'Coy — one lying extended in the shale, and the other coiled up. 



