When in course of time the third edition of _The Great Ice Age_ was sold out, he considered very carefully whether he should undertake a revision of the book, bringing it up to date by incorporation of the most recent additions to our knowledge of the glacial period. Advancing years made him to some extent reluctant to undertake so formidable a task, and he felt also that in his interpretation of the chief events of this chapter of geological history he had no radical alterations to make. This, as we have already said, is sufficiently clear from his attitude in his Munro lectures. Moreover, the whole subject was highly controversial, and he greatly disliked fighting the old battles over again. At one time he was seriously thinking of writing a short work outlining the most important recent advances in glacial geology, but the intention was never carried into effect. Problems of tectonics and of the relations between geological structure and the surface configuration of the earth at the present time always possessed a strong fascination for him, and in his college lectures were favourite topics for discussion. Belonging to both geology and geography, these were subjects in which all his powers found congenial exercise. The _Scottish Geographical Magazine_ contains many papers from his pen dealing with physical geology, and the last of these which he wrote was on “The Deeps of the Pacific Ocean and their Origin.” In this paper he advocated a new interpretation of these great submarine depressions, and as his views were not in accordance with those of Prof. Suess of Vienna, as expounded in his great work _The Face of the Earth_, this paper was the occasion of a long and friendly correspondence with the eminent Austrian geologist (an Englishman by birth). Prof. Geikie had always been a great admirer of Suess and a close student of his writings, and both were attracted by the same kind of problems. In 1911 Prof. Geikie had written a paper on the “Architecture and Origin of the Alps” which appeared in the _Scottish Geographical Magazine_, and ten years previously more than one paper on the origin and structure of mountains had been contributed by him to various journals. He now determined to use the materials he had collected for the preparation of a book which was ultimately issued under the title _Mountains: their Origin, Growth, and Decay_. As usual he did not despise the non-scientific reader, but made his exposition of the subject so simple and clear that all could apprehend his meaning. A vast amount of important work had been done on the geological structure of the Alps during the previous ten years, and in addition to reading the literature carefully, Prof. Geikie visited Switzerland to make himself familiar with the scenes he described, and to enable him to form an opinion on the theories advanced, based on personal examination of some of the best sections. At the same time he