The author commenced by alluding to the disposition of geologists to draw conclusions of a general nature too hastily from the facts observed by them, illustrating this remark by referring to the various opinions successively promulgated, not only by geologists generally, but even by the same geological writer, on the subject of the till or boulder clay, the gravel, and sand, by which Great Britain is every where more or less covered. At one period, all these superficial deposits were referred to the action of water alone; now it is the fashion to explain them by the agency of glaciers.