Having already expounded in his previous works the essential phenomena of glaciation, he devotes this book especially to the consideration of many questions of subordinate importance, though in themselves deserving of full consideration. The interglacial problem, of course, comes up for treatment, but he has not much to say of it that is really new to his readers. It is interesting to note, however, that less insistence is now laid on the Scottish evidence in favour of interglacial periods, and the British evidence in general, and more is said of the interglacial beds of Germany, France, Italy, Switzerland, and other European countries. The feeling seems to have arisen in the author’s mind that much of the British evidence was not so strong as to carry conviction, and the work of continental geologists was rapidly adding details of the highest significance to the store of accumulated observations in favour of repeated glaciations of Northern Europe. We may readily believe also that he felt it desirable to enforce on the minds of his readers the value of much recent research done by his fellow-scientists in other countries. Many British geologists assumed and still maintain a very sceptical attitude regarding the value of the British evidence for interglacial periods, and Prof. Geikie was undoubtedly right in appealing rather to well-established facts in adjacent countries than attempting to discuss the minutiæ of sections often of a temporary nature and by no means well-exposed, which were familiar to many of his British readers. It is not to be supposed, however, that he had changed his ground; to the last he maintained the validity of the British evidence for interglacial periods, though in some parts of it modifications of his original statements might have become necessary. In the nature of things the evidence collected from so small an area as Scotland was sure to be incomplete, and to treat Great Britain as a region apart was more likely to lead to error than to correct results.