Ixxviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



determines the age of all the volcanic beds above the lowest leaf-bed. 

 There is also strong evidence of the volcanic action having been sub- 

 aerial. The author also concludes that the leaves were accumulated 

 during successive autumns in the still water of some shallow lake, on 

 the spot in which they were afterwards covered up by an overflow of 

 volcanic mud, or showers of volcanic ashes. The tertiary origin of 

 these beds is also proved incontestably by the conglomerate of flints 

 into which, as above mentioned, the volcanic bed, immediately beneath 

 the upper leaf-bed, gradually passes. The author considers it pro- 

 bable that the flints and the matrix in which they are imbedded were 

 ejected together as a muddy flood, which spread itself over the sur- 

 rounding surface. 



In the geological events of which we have such distinct evidence 

 in the paper before us, and in that by Prof. E. Forbes previously no- 

 ticed, we have very interesting and instructive portions of the geolo- 

 gical history of this region since the commencement of the Oolitic 

 period. We have, first, the deposition of the lower Oolites, probably 

 in a sea of considerable depth, succeeded by the sudden overflow of 

 volcanic matter, and the subsequent elevation of the surface, which 

 placed it under approximately subaerial conditions, in the portion of 

 the region, at least, in the neighbourhood of the Isle of Skye. There 

 was then a depression and subsequent deposition of the upper Oolites, 

 followed again by an enormous volcanic eruption, of which the Amyg- 

 daloidal Trap of that island is a portion. How far the Cretaceous 

 series may have extended over this region we know not ; but the 

 flint-conglomerate, mentioned by the Duke of Argyll, is strongly in- 

 dicative of its having extended at least to the island of Mull. His 

 Grace points out the analogy which the upper beds of Trap at Ard- 

 tun bear to the basalts on the coast of Antrim, while he assimilates 

 the lowest bed to the basaltic masses of Stafl'a. It is probable, then, 

 that during the Cretaceous period, a part of this region, at least, un- 

 derwent a great depression. After the deposition of the Chalk, came 

 the outpourings of volcanic matter on the north coast of Ireland, and 

 at the islands of Mull and Stafl'a, assuming the above-mentioned rela- 

 tion between the Traps of those islands. Whether these outpourings 

 belong to the same portion of the Tertiary period may be doubtful, 

 especially if the Ardtun beds be assumed to be Miocene, as Prof. 

 Forbes is disposed to regard them. If the Antrim beds be not 

 Eocene, the surface of the newly-deposited Chalk must probably 

 have been elevated so as to prevent Eocene deposition upon it, and 

 then again depressed to receive on its surface the mass of ejected Trap- 

 rock superincumbent upon it. Again, on the coast of Mull, the sur- 

 face, having been subaerial at the Miocene epoch, must have been 

 again submerged during the Pleistocene period ; and finally the whole 

 region must have been again raised to its present elevation. Such 

 are the oscillations which we are enabled to recognize in this region ; 

 possibly, however, they may form only a small part of the whole 

 series of similar movements. 



We are much indebted to the noble author of this paper for the 

 interesting facts which he has brought under our notice ; and, let me 



