EUROPE BEFORE ARRIVAL OF MAN 



more, and 83 feet 4 inches in length, and stretch 

 it along the wall of a large hall, or round the 

 walls of an apartment somewhat over 20 feet 

 square. Recall to memory the days of your 

 boyhood, so as to get some adequate concep- 

 tion of what a period of a hundred years is. 

 Then mark off from one of the ends of the 

 strip jV of an inch. The ^ of the inch will 

 then represent one hundred years, and the en- 

 tire length of the strip a million of years. It is 

 well worth making the experiment, just in order 

 to feel the striking impression that it produces 

 on the mind." Mr. Croll further reminds us 

 that if we could see side by side a million of 

 years as represented in figures and a million of 

 years as represented in geological work, our 

 respect for a unit with six ciphers after it would 

 be notably increased. " Could we stand upon 

 the edge of a gorge a mile and a half in depth, 

 that had been cut out of the solid rock by a 

 tiny stream, scarcely visible at the bottom of 

 this fearful abyss, and were we informed that 

 this little streamlet was able to wear off annually 

 only ^ of an inch from its rocky bed, what 

 would our conceptions be of the prodigious 

 length of time that this stream must have taken 

 to excavate the gorge? We should certainly 

 feel startled when, on making the necessary 

 calculations, we found that the stream had per- 



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