Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/36



I shall now proceed to consider the nature of the rocks which compose this island, in as regular a detail as my opportunities and its intricate and unsettled geography allowed me to observe and record them.

It was not without repeated efforts and much careful tracing of the successions of the stratified rocks through coasts difficult in themselves and far distant from each other, that I was able to discover the key to the very great obscurity in which these are involved. It will be seen that there are yet points unexplained, particularly respecting the trap rocks, a circumstance which will not surprise geologists who know that to patience, toil, and good seasons, must often be superadded good fortune; the casual discovery of perhaps the only point over a wide tract which is capable of yielding the explanation of which we are in pursuit.

As the mica slate and its associate the quartz rock are the most ancient of those which I have ascertained in Sky, I shall commence from them as the foundation of the whole structure. I have associated these rocks in this manner, because I have generally found them alternating, and bearing a common relation both to those which appear to hold a deeper, and to those which have a more superficial position with regard to them, the granite and the stratified rocks; but I need not repeat these reasons here as I have discussed them at sufficient length in the account which I formerly gave of quartz rock, I have not however traced any decided alternation between these two rocks in this island, nor, as far as I have observed, is it likely that any alternation will easily be traced, since the beds of both are far less regular than is usual when they are associated in an alternating orders The mica slate is found occupying the district of Sleat, and it extends from the point of that promontory to an irregular line drawn between Loch Eishort and Loch