5 88 THE POPULAR SCIENCE MONTHLY. 



that man could not have originated at the foot of the glacier. The ice 

 must have met him toward the close of the Tertiary period in the 

 northern parts of Asia and America, and forced him southward ; or, 

 at a later time, it must have found him on the main belt of this conti- 

 nent. The Tertiary origin of man is presupposed, from the fact that 

 he had submitted to a race-modification fitting him to endure the 

 cold. 



Let us consider for a moment what this glacial epoch really was. 

 As to its occurrence, the ice has left its mark on the rocks, and we see 

 its moraines and transported bowlders over a vast portion of this con- 

 tinent from Virginia to the Pacific. There is no doubt that a vast 

 ice-sheet, a continental system of glaciers, was here at a distant time. 

 It has transported masses of rock, and left them on the summit of 

 Mount Washington, where they still remain, and to do this it must at 

 one time have overtopped the mountain. The ice gradually spread 

 from the north, and its progress was slow, as we judge of time so 

 slow that it must have seemed immovable and unchanging from year 

 to year, to the man of the epoch, just as it seems to us now ; and just 

 as slowly as it advanced it retired again to where it is to-day. 



The glacial epoch comes in between the present or Quaternary 

 division of time and the Tertiary. In order to estimate its effects, 

 we must briefly consider the aspect of the earth before its advent and 

 in the preceding epochs. 



There are two principal conclusions to be drawn from an examina- 

 tion of the fossil remains of plants and animals during the Tertiary. 

 The first is, that the climate over the largest portion of the globe 

 was then equable. There were then apparently no seasons the sum- 

 mer seems to have been perpetual. The proof of this lies in the fact 

 that there was a general distribution of plants and animals over the 

 whole surface. In Greenland and Arctic America there were forests 

 of trees, as attested by the remains of their trunks, stumps, and 

 leaves. The same regions reveal to us coal-fields, and the fossil re- 

 mains of reptiles like those we find in beds of the now temperate 

 zone. We find beds of coal on desolate islands in the Southern 

 Pacific Ocean, islands so cold and barren as to afford now but weak 

 and little plants ; whereas these beds of coal attest the presence once 

 of a luxurious vegetation, of which they are the remains. 



The second conclusion is, that the Tertiary was the richest in the 

 number and kinds of the higher animals as compared with the present 

 or any preceding geological period in the earth's history. Then our 

 Territories supported all the various kinds of animals, for instance, 

 which culminated in the horse. The remains of hundreds of species 

 of animals have been collected by Prof. Marsh from a region which 

 now supports but very few. 



Prof. Huxley has, by his now famous lectures in New York City 

 the past year, made popularly known the discoveries of fossils by 



