It would lead me too far, were I to describe also the course of the great ancient glaciers which descended from the southern slopes of the Alps into the plain of Northern Italy. Moreover, these boundaries are not yet ascertained with the same degree of accuracy as those of the northern and western slopes; though very accurate descriptions of some of them have been published, with illustrations on a large scale, by MM. Martins and Gastaldi, and of others by Professor Ramsey. I have myself examined only the upper part of that of the valley of Aosta. The evidence concerning the ancient glaciers of the Alps, especially within the limits of Switzerland, is already so full that it affords ample means for a comprehensive general view of the subject. It is frequently the case, that, when a stretch of time or space lies between us and a matter we have once studied more closely, it presents itself to us as a whole more vividly than when our nearness to it forced all its details upon our observation. In my present position, now that the lapse of many years separates me from my personal investigations of the ancient and modern glaciers, and I look back upon them from another continent, it seems to me that I have, as it were, a bird's-eye view of their whole extent; and I confess that this distant retrospect of the subject has been to me almost as fascinating as were the researches of my earlier years in the same direction. I wish that I could present it to the minds of my readers with something of the attraction it possesses for me. I trust, however, that I have made it plain to them that the great mountain-chain of the Alps has been a central axis from which immense glaciers at one time descended in every direction, not only to its base, beyond which the lowlands extend in flat undulations, but to a greater or less distance over the adjoining plains; while at present they are confined to the higher valleys. So far, then, notwithstanding the extraordinary difference in their dimensions, at the time they reached the Jura and the plain of Northern Italy, when compared with what they are now, they seem directly connected with the Alps, and the mountains appear as their birthplace; so much so that the first attempts at a generalization concerning their origin started from the assumption that they must have been formed between the high ridges from which they seem to flow down. These facts, then the only ones known concerning a greater extension of the glaciers, naturally led to the views advocated by M. de Charpentier. My own theory was also at first, that the upheaval of the Alps must, in some way or other, have been connected with these phenomena. But it soon became evident to me that these views were inadequate to account for the former presence of extensive glaciers in other parts of Europe; and even within the range of the Alps there were insuperable objections to their final admission. If the ancient glaciers