It is best to state frankly at the outset that this topic is one of the great battle-grounds of science to-day, and that there are as yet but few points well settled in regard to it. One needs but attempt to read the literature on this subject to become quickly impressed with the necessity of making haste slowly in forming any conclusions. He must invoke the aid of the astronomer, geologist, physical-geographer, and physicist. Yet we must not suppose that questions relating to the Glacial Age are so abstruse that they are of interest only to the scholar. On the contrary, all ought to be interested in them. They open up one of the most wonderful chapters in the history of the world. They recall from the past a picture of ice-bound coasts and countries groaning under icy loads, where now are harbors enlivened by the commerce of the world, or ripening fields attesting the vivifying influence of a genial sun. Let us, therefore, follow after the leaders in thought. When we come to where they can not agree we can at least see what both sides have to say. Somewhat at the risk of repetition, we will try and impress on our readers a sense of the reality and severity of the Glacial Age. There is danger in regarding this as simply a convenient theory that geologists have originated to explain some puzzling facts, that it is not very well founded, and is liable to give way any day to some more ingenious explanation. On the contrary, this whole matter has been worked out by very careful scholars. “There is, perhaps, no great conclusion in any science which rests upon a surer foundation than this, and if we are to be guided by our reason at all in deducting the unknown from the known, the past from the present, we can not refuse our assent to the reality of the Glacial Age of the Northern Hemisphere in all its more important features.2 At the present day glaciers do exist in several places on the earth. They are found in the Alps and the mountains of Norway, and the Caucasus, in Europe. The Himalaya mountains support immense glaciers in Asia; and in America a few still linger in the more inaccessible heights of the Sierra Nevada. It is from a study of these glaciers, mainly however, those of the Alps, that geologists have been enabled to explain the true meaning of certain formations they find in both Europe and America, that go by the name of drift.