4 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 24, 



series, near its base, contains coarse conglomerates of well-rounded 

 white and pink quartz-pebbles ; but they differ markedly in this, 

 that on the Logan water no unconformability was observed between 

 the bottom of the Old Eed Sandstone and the Silurians containing 

 the Eiirypteri, &c., which are referred by Sir B,. Murchison, on 

 palaeontological grounds, to the Ludlow period. I have compared the 

 Portencross Silurians with those of the south of Ayrshire ; but this 

 conclusion, resting solely on mineral characters, cannot rise higher 

 than a mere probability. 



In the elaborate memoir* on the geology of the Isle of Arran, by 

 Sedgwick and Murchison, it is shown that the axis of elevation of 

 the Old Red Sandstone, the coal-measures, and the red sandstones 

 which are superior to the coal, passes through North Sannox on the 

 coast, and that these formations dip very regularly N.N.W. and 

 S.S.E. respectively on the two sides of this axis. The strike of 

 the beds, therefore, is E.N.E. ; and if the axis be prolonged on the 

 map from North Sannox to the coast of Ayrshire, it will strike the 

 coast close to Portencross, where the above-described protrusion of 

 Silurian rocks occurs. The coincidence is too striking to be 

 accidental : it is clear that the exertion of force which has elevated 

 the Devonian beds and the coal-measures in Ayrshire is the same 

 as that which has produced the same effect in Arran, distant about 

 10 miles. But it is to be observed also, that this axis runs E.IST.E., 

 that is to say, exactly parallel to the strike of all the lower Silurian 

 rocks in the south of Scotland. Now it is certain, from many 

 sections described by many different observers, that the Silurian 

 rocks had undergone upheavals and convolutions, and had had their 

 present strike impressed upon them, previously to the deposition of 

 the Old Red Conglomerates, — while the facts I have mentioned above 

 prove that an exertion of force very different, indeed, in energy, but 

 exactly corresponding in direction, reoccurred after the close of the 

 Permian period. 



2. On the Kelloway Rock of the Yokkshire Coast. By John 

 Leckenby, Esq. (Communicated by John Morris, E.G.S.) 



[Plates I. II. III.] 

 Among the more interesting features in the geology of the east coast 

 of Yorkshire is the KeUoway Rock, whether compared, in its extra- 

 ordinary development, or in the great variety of its fossils, with its 

 Wiltshire prototype. 



The Kelloway Rock is first seen in the cliff a short distance to 

 the south of Gristhorp Bay, and here, but for its position below 

 the Oxford Clay, and the presence of some characteristic fossils, 

 there is little about the thin band of calcareous pisolite in which 

 these fossils occur to identify it with the ochreous and arenaceous 



* Transact. Greol. Soc. ser. 2. vol. iii. p. 21, 



