A GRASP OF GEOLOGIC TIME. 155 



that bis race was destined to contemplate things in a state 

 of fixity, or moving in ever-repeated cycles; hence every 

 moAentous revolution in terrestrial affairs of which we 

 trace the records must have antedated the advent of man 

 into Europe and Asia, must have antedated the first ap- 

 pearance of man on the earth. It must stretch back into 

 a remote antiquity. When, therefore, we discovered, as 

 we must discover, that man bad been the witness of vast 

 geologic changes, we first, as by an impulse, declared that 

 man's existence mounts also to an antiquity measured by 

 scores of thousands of years.* 



We have learned another lesson in the primer of science. 

 The great tide of events which we have witnessed sweeping 

 down through the ages of palaeozoic and later geologic 

 time is now sweeping past our very doors. It is the same 

 tide: we ourselves are borne upon its bosom. In our brief 

 day we may note a few of the vicissitudes which swell and 

 perpetuate the current. 



What man of adult years does not know some reedy 

 bog which in his boyhood was a skating pond? Who that 

 has attained the years of grandsire has not seen meadow- 

 land in spots which he once knew as reedy bog? The al- 

 luvial meadow has grown from the reeking marsh; the 

 marsh emerged from the shallow lake-bottom by the slow 

 filling of the depression. The whole work is one within 

 the grasp of human comprehension. But the little lake 

 was a vestige of the last inundation of the ocean, which 

 followed the glacial visitation. So the great glacier almost 

 looms into view. 



Tlie traditions of the Greeks preserved the memory of 

 an ancient submergence of the Scythian plains. The vast 

 * Compare the author's Preadamites, ch. xxvii. 



