Page:Proceedings of the Royal Society of London Vol 4.djvu/151

Rh Mr. Darwin's paper, entitled, " On the Parallel Roads of Glen Roy, and other parts of Lochaber, &c.," was resumed, but not con- cluded.

Commander Henry Mangles Denham, R.N., and Richard Drew, Esq., were balloted for, and duly elected into the Society.

The reading of a paper, entitled, " Observations on the Parallel Roads of Glen Roy, and of other parts of Lochaber, with an attempt to prove that they are of Marine Origin." By Charles Darwin, Esq., M.A., F.R.S., Sec. Geological Society, was resumed and con- cluded.

The author premises a brief description of the parallel roads, shelves, or lines, as they have been indefinitely called, which are most conspicuous in Glen Roy and the neighbouring valleys, re- ferring for more detailed accounts to those given by Sir Thomas Lauder Dick, in the Transactions of the Royal Society of Edin- burgh, and by Dr. MaccuUoch in those of the Geological Society of London. Both these geologists endeavour to explain the formation of these shelves on the hypothesis of their resulting from depositions at the margin of lakes, which had formerly existed at those levels. The author, however, shows that this hypothesis is inadmissible, from the insuperable difficulties opposed to any conceivable mode of the construction and removal, at successive periods, of several bar- riers of immense size, whether placed at the mouths of the separate glens, or at more distant points. He does not, however, propose the alternative, that the beaches, if not deposited by lakes, must of necessity have been formed by channels of the sea, because he deems it more satisfactory to prove, from independent phenomena, that a sheet of water, gradually subsiding from the height of the upper shelves to the present level of the sea, occupied for long periods not only the glens of Lochaber, but the greater number, if not all the valleys of that part of Scotland ; and that this water must have been that of the sea. It is argued by the author, that the fluctuating ele- ment must have been the land, from the ascertained fact of the land rising in one part, and at the same time sinking in another ; and therefore, that this change of level in Scotland, attested as it is by marine remains being found at considerable heights both on the eastern and western coasts, implies the elevation of the land, and not the subsidence of the surrounding waters. The author next shows, that in all prolonged upward movements of this kind, it might be predicted, both from the analogy of volcanic action, and from the occurrence of lines of escarpment rising one above the other in certain regions, that in the action of the subterranean im- pulses there would be intervals of rest. On the hypothesis that the