We are all familiar with the general conclusion arrived at by geologists that our earth has experienced many climatic changes. There have been times when genial conditions ranged up to the highest latitudes, and times also when the cold of the arctic regions descended to what is now our temperate zone. The cause or causes of those remarkable vicissitudes still baffle research. Many explanations have been advanced, some highly improbable, others perhaps more likely, while of yet others it may be said that possibly they contain a certain amount of truth. But no one theory or hypothesis has succeeded in gaining general assent, and we shall not therefore at present concern ourselves with any. In place of reviewing hypotheses and speculations, I shall limit myself to a survey of certain facts connected with the later geological history of our continent, the meaning of which is more or less apparent. The evidence referred to leads to the conclusion that Middle Europe has within the human per