Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/46

From Wikisource
Jump to navigation Jump to search
This page has been proofread, but needs to be validated.


found, formed of large gravel or even of fragments, but I have not seen either in Sky, in Soa, or in Rum, any regular beds of conglomerate connected with it, although I have in these situations had repeated access to the whole thickness of the rock. Although the general colours of this rock are such as I have described, yet it seems occasionally, like the lowermost red sandstone in other places, to contain portions of a different complexion; one portion of such a bed is seen under Garsven opposite to Soa, where it is of a white colour and intermixed with decomposed felspar, yet still exceedingly compact. Pebbles of quartz and granite are imbedded in some of its laminæ. For the sake of those who contend for the doctrine of universal formations of rock, I have recorded the whole of its characters and connections that they may have opportunities of comparing them with those of other similar rocks, and I can only add to what I have here said, that as I imagine Rum and Sky to contain portions of one common bed, so I am inclined to think that the red sandstone which I have found on the western coast of Scotland in various places, from Loch Ewe to the Ru Storr, appertains to the same series of beds. It is still the same sandstone, as I imagine, which extends to the east coast and finally to Orkney.

The next bed in order is a bed of limestone, the investigation of which was attended with more labour and doubt than that of all the other rocks of Sky, and of which the history I am about to give cannot appear less credible to others than it did at first to myself: the demonstration which I at length procured and shall now lay down is however such as to admit of no dispute. It is important in a general view since it shows us how little reliance can be placed on internal characters in assigning the positions of rocks in the system, and since it may possibly lead the way to the explanation of those anomalous limestones to which the examples occurring near Plymouth,