Pseudo-Glacial Phenomena

Abstract

I BEG to call the attention of geologists to the following facts:—On the north-east coast of Australia, at the end of Trinity Bay, about lat. 17° S., there are steep ranges of granite abutting on the sea-margin. Every rainy season (December, January, and February) immense quantities of the granite become loosened from the upper part of the mountains, and fall in extensive landslips down the sides. These landslips or rockslips are so numerous, that in fine weather they are most conspicuous objects on the sides of the hills, and look like dry water-courses. One of these rockslips I witnessed at Cape Grafton, from a distance of three miles. The noise was terrific, and the ground trembled as though from an earthquake. On examining the blocks of granite which had slipped to the bottom of the ravine, I found many of them with their sides grooved and scratched, and one fragment was as beautifully polished on one side as if it came from the hands of a lapidary, excepting, of course, the scratches and grooves. In the course of a few centuries, much of the range will be worn away, and its sides represented by an alluvial deposit mainly consisting of angular boulders of every size and shape, many of which will be polished, scratched, and grooved. There are very few geoloiogists who would not call it a glacial drift, even now, were not the cause so evidently before them. Will this help to explain tho e so-called drifts, which, like this instance, are found far within the tropics?