SIR HENRY HOWORTH wishes to continue the discussion of glaciation in the pages of NATURE, but I find in his last letter very good reason why this cannot be done. No discussion can lead to definite results unless the parties to it accept as data what they themselves have recently and deliberately admitted. But when I stated that the Rhone glacier did reach the Jura, and deposit on it erratic blocks between Geneva and Soleure, I did so because it was one of the data already admitted by Sir H. Howorth. In his “Glacial Nightmare,” pp. 169-173, he gives a full summary of Charpentier's first memoir on the erratic blocks of Switzerland, describing the glacial phenomena exhibited along the whole course of the old glaciers from the Alps to the Jura, and showing that they “even climbed that range and went over to the other side of it.” Sir H. Howorth then says: “I have quoted at considerable length from this excellent memoir, because I look upon it as having definitely applied inductive methods to this question with results which are for the most part sound and unanswerable.” (Italics mine.) In the same chapter (pp. 195-202) Charpentier's second memoir is summarised still more fully, and his general conclusion is thus quoted: “It goes without saying that not only all the valleys of the Valais were filled with ice up to a certain height, but that all lower Switzerland, in which we find the erratic debris of the Rhone valley, must have been covered by the same glacier. Consequently all the country between the Alps and the Jura, and between the environs of Geneva and those of Soleure has been the bed of a glacier.” Agassiz and other writers are quoted as giving further evidence of the same kind. Nowhere in the whole of this chapter can I find a single objection to the conclusions of the chief writers quoted, and the concluding paragraph, at p. 208, frankly accepts them. It declares that they are supported by “every form of converging evidence,” and that—“So far there is no question at issue.” Yet, when I take these same conclusions of Charpentier as admitted data, Sir H Howorth says: “This form of dogmatic argument is assuredly incomprehensible!” Charpentier's proof that the Rhone glacier reached Soleure, was, a year ago, “sound and unanswerable,” and was an example of “definitely applied inductive methods”; but when I accept these same results as something to reason upon, I am told that I am making use of “hypotheses outside the laws of nature.” I have now justified my opening statement that a discussion carried on in this manner can serve no useful purpose.