Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/185

 sandstone, and which increase the difficulty of distinguishing between the two substances at that distance from which alone they are visible. Hence it is with some doubt that I must speak of the absolute nature of the whole strata between Portree and Holme; a matter fortunately of no serious moment, as geologists are well aware of the intimate connection subsisting between these strata, which have been fully examined and described in many parts of the British islands.

Alternations of micaceous shale and of brown sandstone are found in the calcareous beds, of which the colour and composition vary materially, although the predominant colour is smoke-grey, the aspect earthy, and the composition argillaceous. The only organic remains which I could find among them were a large ammonite and a belemnite often exceeding a foot in length. As far as I can discover, our conchologists have not yet ascertained these species or distinguished them by specific names.

But it is unnecessary to enter into minute details respecting this limestone, since it must be already seen that it belongs to the lias, a rock well known to geologists, and already often described under all its varieties of aspect.

I shall take some future opportunity of describing this important series as it occurs throughout the western islands, since it is so dispersed as to involve the history of many of them, and to render it impossible to give an adequate account of it in a paper so local as this.

Proceeding northwards along this shore, it appears that the beds which follow are superior in position to the preceding. This should result from their general dip, but it cannot be distinctly ascertained. Here, common shale begins to appear in alternation with the other substances, and the quantity of siliceous schistus