while, I am not sorry that just at this moment, when recent investigations and publications have aroused new interest in the glaciers, the course of these articles brings me naturally to a discussion of the subject in its bearing upon geological questions. I shall, however, address myself especially, as I have done throughout these papers, to my unprofessional readers, who, while they admire the glaciers, may also wish to form a general idea of their structure and mode of action, as well as to know something of the important part they have played in the later geological history of our earth. It would, indeed, be out of place, were I to undertake here a discussion of the different views entertained by the various students who have investigated the glacier itself, among whom Dr. Tyndall is especially distinguished, or those of the more theoretical writers, among whom Mr. Hopkins occupies a prominent position. Removed, as I am, from all possibility of renewing my own observations, begun in 1836 and ended in 1845, I will take this opportunity to call the attention of those particularly interested in the matter to one essential point with reference to which all other observers differ from me. I mean the stratification of the glacier, which I do not believe to be rightly understood, even at this moment. It may seem presumptuous to dissent absolutely from the statements of one who has seen so much and so well as Dr. Tyndall, on a question for the solution of which, from the physicist's point of view, his special studies have been a far better preparation than mine; and yet I feel confident that I was correct in describing the stratification of the glacier as a fundamental feature of its structure, and the so-called dirt-bands as the margins of the snow-strata successively deposited, and in no way originating in the ice-cascades. I shall endeavor to make this plain to my readers in the course of the present article. I believe, also, that renewed observations will satisfy dissenting observers that there really exists a net-work of capillary fissures extending throughout the whole glacier, constantly closing and reopening, and constituting the channels by means of which water filtrates into its mass. This infiltration, also, has been denied, in consequence of the failure of some experiments in which an attempt was made to introduce colored fluids into the glacier. To this I can only answer, that I succeeded completely, myself, in the self-same experiments which a later investigator found impracticable, and that I see no reason why the failure of the latter attempt should cast a doubt upon the former. The explanation of the difference in the result may, perhaps, be found in the fact, that, as a sponge gorged with water can admit no more fluid than it already contains, so the glacier, under certain circumstances, and especially at noonday in summer, may be so soaked with water that all attempts to pour colored fluids into it would necessarily fail.