THE EARLY MAN OF NORTH AMERICA. 589 



Prof. Marsh in the Western cretaceous and tertiary beds. It remains 

 but to add a link to the genealogy of the horse, discovered by Prof. 

 Marsh since the time when Prof. Huxley lectured. You will remem- 

 ber that Prof. Huxley showed that there was a regular series of pro- 

 gressive forms from the Eocene Orohippus to the recent horse, in the 

 character of the teeth, and in the structure of the fore and hind feet. 

 There was more than that, perhaps, when we consider that there was 

 an increase in size, in length of limb, and consequent activity, of the 

 animal. In the Orohippus we have four toes on the front and three 

 on the hind limbs, and so far Prof. Huxley was able to trace the 

 genealogy of the horse with its single toe down toward the type of 

 mammals with five toes. But we can now go a little further in the 

 process of the evolution of the horse. In New Mexico, in a fossil 

 bed, the horizon of which is below that in which the Orohippus oc- 

 curs, Prof. Marsh has found the remains of an animal which he calls 

 the Eohippus. The feet, which are very much like those of the Oro- 

 hippus with their well-developed four toes in front and three behind, 

 show a rudiment of the outer or fifth toe. The Eohippus was an ani- 

 mal as large only as a fox, though perhaps a little stouter, and, from 

 the structure of its limbs, is the nearest yet discovered progenitor of the 

 horse to the usual five-toed mammalian type. And in his lecture Prof. 

 Huxley anticipated the actual discovery of the Eohippus by showing 

 that such a form must have existed as the progenitor of the four-toed 

 horse. Animals, also, which were the prototypes of the camel, have 

 been there discovered by Prof. Cope. Strange if, at the time when 

 the whole earth presented such a profusion of vertebrate life, man 

 should not also have appeared upon the scene ! The conditions were 

 never so perfect, either before or since. Over this field of luxu- 

 riant life, the cold broke in. The ice commenced to form, and then 

 to move in masses, scattering or extirpating the plants and animals. 

 There were migration and adaptations. Such animals and plants as 

 could adapt themselves to the cold persisted. To probably smooth- 

 skinned elephantoid types, the woolly mammoth succeeded in the 

 northern regions. Stunted willows replaced tree-like plants of the 

 same botanical family. If it met man, it must equally have modified 

 his habits of life and his physical characteristics. It must have made 

 something like an Esquimaux of him. As to the cause of the glacial 

 epoch itself, from a study of all that has as yet been said on the sub- 

 ject, we must ascribe it to upheavals of land in the north, and a 

 change, perhaps a consequent change, in the earth's position toward 

 the sun. There was, it seems, an elevation of the earth's crust and a 

 variation in the earth's axis; which latter, in order to have produced 

 the climatic effects of former geological periods, must apparently have 

 been more nearly perpendicular than it now is. It is probable that 

 oscillations then set in, which may make a second glacial epoch prob- 

 able, although of this we cannot speak with certainty. Evidence is 



