In addition to these, there was also a large number of animals whose home is in the temperate regions of the earth—animals that thrive in neither extremes of heat and cold. This includes a great many animals of the deer kind, several varieties of bears and horses; in fact, the majority of those with which we are acquainted.13 Now, what conclusion follows from this assemblage of animals? Many theories have been put forward in explanation. It has been suggested that Europe at that time had a climate not unlike that of some portions of the earth at present; that is, a long and severe Winter was followed by a short but warm Summer. During the Winter reindeer and other northern animals would press from the north in search of food, but would retire on the approach of Spring, when their feeding grounds would in turn be occupied by bisons and animals of a southern habitat. In confirmation of this view it is pointed out that a vast collection of bones, from the bottom of a sink-hole or pond in Derbyshire, England, conclusively show that in the summer-time it was visited by bisons with their calves, and in Winter by reindeer.14 This theory is open to a great many objections. As is well known, some animals make quite extensive migrations annually, but we can scarcely believe that heavy, unwieldy animals like the hippopotamus, were then such industrious travelers as to wander every year from Italy to Northern England and return.15 But the very ground on which this theory rests, that of strongly contrasted summers and winters, could not be true of Europe or the western portions of it, owing to the presence of the Atlantic Ocean, and the influence which it inevitably exerts on the climate.16 We see, then, that the presence of these different animals can be explained only by supposing great secular changes in climate. Let us see if we can strengthen this view by an appeal to the vegetation of this period.