The important new evidence brought to light was not wholly the result of geological investigation, though much of it was strictly of the kind to which Prof. Geikie had appealed. Most striking perhaps were the descriptions of the glacial phenomena of the Alpine valleys which Profs. Penck and Brückner published in a famous volume in 1909. This work was most appropriately dedicated by the authors to Prof. James Geikie. It is probably the most notable contribution to the literature of glacial geology in the last twenty years, and although it has not escaped criticism, it has produced in the minds of impartial readers a firm conviction of the occurrence of glacial and interglacial periods so far as that part of Europe is concerned. Prof. Geikie was familiar with some of the evidence from the Alpine chain when he was writing the third edition of _The Great Ice Age_; some of the facts had led geologists to postulate the existence of interglacial periods as long ago as the middle of last century; but he watched with great pleasure the gradual accumulation of observations added to previous knowledge by Penck and Brückner, and for many years he maintained an active correspondence with these investigators. In America, also, the opinion was gradually gaining strength that the Ice Age was marked by several prolonged intervals of warmer conditions; and in France, Germany, and Scandinavia many geologists were added to the ranks of those who maintained the importance of interglacial periods.