338 PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [Feb. 26, 



on one side of a valley from mica-slate, and on the other from a boss 

 of coarse red granite rising through the slate. It seems a legitimate 

 conclusion from the occurrence of these breaks in the usual suc- 

 cession in one part of the Liassic area, that denuding causes may 

 have similarly acted in another, and so have removed the inter- 

 mediate formations from over the Cambrian sandstone in Skye and 

 Eaasay before the Jurassic beds were laid down. 



The Lower Lias has been identified on Loch Sligachan and in 

 Eaasay, the existence of the Bhaetic beds in the latter rendered 

 almost certain, the Middle Lias traced in its full development 

 northwards, and the Upper Lias traced through a long horizontal 

 distance ; the members of the Inferior Oolite have been distinctly 

 separated, and the characters shown to be persistent; the area 

 of the Middle Oolite has been extended, and its beds traced from 

 the Loch-Staffin cliffs by the interior part of the country round 

 the base of the Storr mountain into the area of the Portree Oolites, 

 where the characters and fossils are identical. From beds whose 

 fossil contents were before unknown, a large collection of fossils, 

 embracing many new species, has been obtained, whose relations 

 with those of other areas present many points of interest. 



The lithological characters of the beds have a remarkable simi- 

 larity throughout, and a close resemblance to the structure of the beds 

 on the Yorkshire coast, as shown in the character of the great 

 sandy Oolite, with its included coal-beds and jet, those of the Upper 

 Lias, though of such insignificant thickness, and the striking similarity 

 of the Oxford clay. All this indicates a wonderful resemblance in the 

 sediments carried down into two areas divided by half the length of 

 Great Britain, and a striking similarity in the productions of land- 

 surfaces so widely separated, by which the coal- and jet-beds, the 

 Oycas and the fern were supplied. Where, we may ask, lay the land 

 which supplied these growths, and the vast alternations of argilla- 

 ceous, sandy, and calcareous beds which we find within the area ? 

 That changes took place in the land-surfaces themselves during the 

 period of the deposits is evident by the change from marine to 

 estuarine and almost freshwater conditions, of which the evidence 

 remains to us in the marine fossils of Staffin, the estuarine towards 

 Portree, and those of a freshwater character at Loch Bay and Yater- 

 stein. Oscillations of the land, the deepening and shallowing of 

 water would soon bring about such a change in the fauna. 



And, lastly, as regards the intrusive sheets of trap, it appears 

 from the facts stated regarding the three sections on which they 

 are met with, that they are of later age than the Jurassic beds amid 

 which they lie ; the beds on either side are in every case altered by 

 them ; they are thus certainly not of Oolitic age, as has been sup- 

 posed; that is, they were not injected after one bed had been thrown 

 down, and before the next overlying was deposited. Of how much 

 later a date they may be than the Oolitic strata it is difficult to 

 decide, the Camus-Inivaig section being the only one which affords 

 any evidence. Doubtless they were formed at great depths ; and to 

 this their uniformly crystalline character may be due, as well as to 



