~INTRODUCTION 5 
not yet ready to take this step; just as in the early 
days of astronomical science there were those who 
held to the long-abandoned belief that the stars were set 
in the firmament, but a short distance above the earth. 
Now, even the youngest thinker gazes into the starry 
vault, awed by the grandeur of the fact, that if one of 
those twinkling bodies had been extinguished a century 
ago, it would still be visible; because, even with the 
rapidity of the passage of light, time enough has not 
yet elapsed to telegraph the fact to the earth. 
So the geologist looks at the hill and fully realizes 
the insignificance of the human mind, when he thinks 
that this same hill, with nearly the same form, wit- 
nessed the coming and going of the red man; that it 
was still a hill before the human race appeared upon 
the earth; and that, during all this time, it has been 
slowly changing, with a life history to be measured in 
tens or even hundreds of thousands of years. 
Astronomers demand that we discard the human con- 
ception of distance and think of millions of miles: geol- 
ogists demand the same for time. Our experience is 
too limited for us to truly appreciate these conceptions, 
for a century seems a very long time, and a thousand 
miles is an immense distance; but if one would come 
in touch with these two broad sciences, geology and 
astronomy, he must first enlarge the power of the mind 
beyond the tiny range which actual experience gives. 
4 
