XXVI.—Account of some Terraces, or ancient Beaches, in the Isle of Jura.

Abstract

To those who speculate on the great general revolutions to which our planet was subjected in the early stages of its existence, it cannot but be interesting to contemplate any changes in the relative situations of land and water, which can be shown to have taken place on a more confined scale, and at a later period. Proofs of some such changes may, I think, be found on the western coast of the island of Jura; and if they have hitherto remained unnoticed, this is to be ascribed, not to the indistinctness of the phenomena which I am about to mention, but to the uninviting aspect of that island, which seen from the Paps, the highest point, and that to which every traveller would naturally repair in the first instance, appears to consist entirely of vast continuous beds of quartz; a detailed examination of which would ill repay the toil and privations, under which alone it could be undertaken, where the surface is so rugged, the accommodations so scanty, and the weather so precarious. My own attention was first drawn to this subject on the summit of Ben an Oir, whence looking in the direction of Loch Tarbert, I observed a number of white patches, which I concluded, in the first instance, to be sheets of water. The telescope undeceived me; but being still ignorant of their true nature, I determined to visit them. On closer inspection, they proved to be blocks of quartz, lying upon six or seven terraces