TIME AND CHANGE 



but a small fraction of one of the days that make up 

 the periods with which the geologist deals. And the 

 span of human life, how it dwindles to a point in the 

 face of the records of the rocks! Doubtless t&quot;he birth 

 of some of the mountain-systems of the globe is still 

 going on, and we suspect it not; an elevation of one 

 foot in a century would lift up the Sierra or the 

 Rocky Mountains in a comparatively short geologic 

 period. 



ii 



It was the geologist that emboldened Tennyson 

 to sing, 



&quot;The hills are shadows and they flow 



From form to form and nothing stands, 

 They melt like mists, the solid lands, 

 Like clouds they shape themselves and go.&quot; 



But some hills flow much faster than others. Hills 

 made up of the latest or newest formations seem to 

 take to themselves wings the fastest. 



The Archaean hills and mountains, how slowly 

 they melt away! In the Adirondacks, in northern 

 New England, in the Highlands of the Hudson, they 

 still hold their heads high and have something of the 

 vigor of their prime. 



The most enduring rocks are the oldest; and the 

 most perishable are, as a rule, the youngest. It takes 

 time to season and harden the rocks, as it does men. 

 Then the earlier rocks seem to have had better stuff 

 in them. They are nearer the paternal granite; and 

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