explained themselves as the shores of a glacial lake, held back in its bed for a time by neighboring glaciers descending from more sheltered valleys. The terraces marked the successively lower levels at which the water stood, as these barriers yielded, and allowed its gradual escape.* (* For details, see a paper by Agassiz on "The Glacial Theory and its Recent Progress" in the "Edinburgh New Philosophical Journal" October 1842, accompanied by a map of the Glen Roy region, and also an article entitled "Parallel Roads of Glen Roy, in Scotland," in the second volume of Agassiz's "Geological Sketches".) The glacial action in the whole neighborhood was such as to leave no doubt in the mind of Agassiz that Glen Roy and the adjoining glens, or valleys, had been the drainage-bed for the many glaciers formerly occupying the western ranges of the Grampian Hills. He returned from his tour satisfied that the mountainous districts of Great Britain had all been centres of glacial distribution, and that the drift material and the erratic boulders, scattered over the whole country, were due to exactly the same causes as the like phenomena in Switzerland. On the 4th of November, 1840, he read a paper before the Geological Society of London, giving a summary of the scientific results of their excursion, followed by one from Dr. Buckland, who had become an ardent convert to his views. Apropos of this meeting, Dr. Buckland writes in advance as follows:-- TAYMOUTH CASTLE, October 15, 1840. . . .Lyell has adopted your theory in toto!!! On my showing him a beautiful cluster of moraines, within two miles of his father's house, he instantly accepted it, as solving a host of difficulties that have all his life embarrassed him. And not these only, but similar moraines and detritus of moraines, that cover half of the adjoining counties are explicable on your theory, and he has consented to my proposal that he should immediately lay them all down on a map of the county and describe them in a paper to be read the day after yours at the Geological Society. I propose to give in my adhesion by reading, the same day with yours, as a sequel to your paper, a list of localities where I have observed similar glacial detritus in Scotland, since I left you, and in various parts of England. There are great reefs of gravel in the limestone valleys of the central bog district of Ireland. They have a distinct name, which I forget. No doubt they are moraines; if you have not, ere you get this, seen one of them, pray do so.* (* Agassiz was then staying at Florence Court, the seat of the Earl of Enniskillen, in County Fermanagh, Ireland. While there he had an opportunity of studying most interesting glacial phenomena. ) But it will not be worth while to go out of your way to see more than one; all the rest must follow as a corollary. I trust you will not fail to be at Edinboro' on the 20th, and at Sir W. Trevelyan's on the 24th. . .