Although these conclusions were only sketched out and not fully stated, it is plain to the reader that already Prof. Geikie had convinced himself of the importance of these facts. And in considering what is probably the most controversial problem which the student of Pleistocene and recent times must investigate, namely, the relation of prehistoric man to the glacial period, he followed the same line of thought, considering that the evidence of the mammalian remains found in caves and river gravels of Northern Europe pointed to the conclusion that there had been great variations of climate. The mixture of northern and southern types of animals was not to be ascribed in his opinion to migrations arising from seasonal changes, but was due principally to alternations of cold and heat, each enduring for a considerable time. He advocated also the existence of man in glacial times, and recapitulating views already enumerated in some papers which he had published in the _Geological Magazine_, he argued that the palæolithic gravels of England were to be regarded as glacial and preglacial, and not, as was widely believed, of interglacial and post-glacial age. Lastly, we may mention a feature of the first edition of _The Great Ice Age_ that was to become more prominent in subsequent editions, the comparative description of the phenomena described by geologists of many different countries. For information regarding England he was largely indebted to his colleagues in the English Survey, principally Green, Tiddeman, and Whitaker. The Swedish, German, Norwegian, and continental deposits generally had perforce to be described from the literature of the subject, a literature already very extensive. Through his whole life Prof. Geikie was a diligent student of the literature of his subject. The most important European languages, as already noted in Part I., he could read with facility, and as he was in constant receipt of copies of glacial papers from their authors, much of his time was taken up with a study of the contemporary literature of glaciation. It was his familiarity with the work of other investigators in this field of scientific research that gave him his position as the representative British glacialist, and made his works so widely read and appreciated by foreign scientific men.