Page:Quarterly Journal of the Geological Society of London, vol. 29.djvu/282

 valleys and anticlinals was obviously the work of the great formative forces by which the whole island had been forced up above the sea, by lateral pressure, squeezing the harder deposits into folds, and these carrying up upon their backs the deep covering of loose material which had lain upon them as sea-bottom. As the land emerged, this loose material was affected by tidal and wave-action, caused to slip and slide down all declivities, even very small ones, and, in doing so, scratched and furrowed the supporting surfaces of rock in a way that he believed it impossible to distinguish from the traces left by similar movements of masses of ice. And if this were so, as like phenomena must be as universal as the emergence of land was everywhere from beneath the sea, so it seemed to him that, so far as the evidences of scratching and polishing or denuding of rocks went, the glacial hypothesis was unnecessary. He admitted the scratching and transporting power of ice as a vera causa of some geological phenomena ; but he believed that its effects had been enormously overrated, and that much had been attributed to its action which, when submitted to the test of " measure, number, and weight," in place of, as was the habit, perpetually dealing with " quality " only, would prove to be physical impossibilities. Thus the work capable of being done upon the ocean- bottom by the grounding of even the largest iceberg, could, when all the dynamic conditions were held in view, be proved to be extremely small. The general facts, as respects the direction of the striation or scratching of the rocks, as well as the direction of transport of boulders in the detritus above, were, for the whole surface of Ireland, that the scratches tended to lines down the great declivities, both laterally and longitudinally, but influenced by a great general trend from the west, and north, and south-west. The lines of boulder-travel had, on the whole, followed the same direction as the scratches. He could not, therefore, admit the views of the author as to the direction of these scratches being on the whole from northeast to south-west as representing the facts. Mr. Mallet referred to a case of a large subangular boulder found in deep clay by himself and Dr. Oldham, stopped in the very act of making an uncompleted groove, and under conditions that forbade any supposition of ice-action or any other source of movement but that of the quasi- fluid movement of the whole mass of clay carrying the boulder with it. He also pointed out that moraines, or masses dropped by ice, could not be distinguished generally from torrentially moved masses of clay, gravel, and rock, or from escars or eddy-bars formed by tidal-stream action, pointing out two cases, one in Wicklow, the other not far from Dublin, both pronounced by Agassiz to be indubitably moraines, but the former being manifestly a torrential bank, the other the effect of a tide-stream eddy when the plain of Dublin was still from 500 to 700 feet beneath the sea-surface.

Mr. Evans disputed Mr. Mallet's conclusions as to the propagation of motion through ice and the effects of grounding icebergs.

Mr. Tiddeman had examined a large portion of the western side of the north of England opposite to Ireland, but did not attribute