302 CLASSICS OF MODERN SCIENCE 

 it constitutes. A Nineveh vessel, a Roman sword awakes in us the 

 conception of grey antiquity. What the museums of Europe show 

 us of the remains of Egypt and Assyria we gaze upon with silent 

 astonishment, and despair of being able to carry our thoughts back 

 to a period so remote. Still must the human race have existed for 

 ages, and multiplied itself before the pyramids of Nineveh could have 

 been erected. We estimate the duration of human history at 6000 

 years ; but immeasurable as this time may appear to us, what is it in 

 comparison with the time during which the earth carried successive 

 series of rank plants and mighty animals, and no men ; during which 

 in our neighbourhood the amber-tree bloomed, and dropped its costly 

 gum on the earth and in the sea ; when in Siberia, Europe and North 

 America groves of tropical palms flourished ; where gigantic lizards, 

 and after them elephants, whose mighty remains we still find buried 

 in the earth, found a home? Different geologists, proceeding from 

 different premises, have sought to estimate the duration of the above 

 creative period, and vary from a million to nine million years. And 

 the time during which the earth generated organic beings is again 

 small when we compare it with the ages during which the world 

 was a ball of fused rocks. For the duration of its cooling from 2000" 

 to 200° centigrade, the experiments of Bishop upon basalt show that 

 about 350 millions of years would be necessary. And with regard to 

 the time during which the first nebulous mass condensed into our 

 planetary system, our most daring conjectures must cease. The his- 

 tory of man, therefore, is but a short ripple in the ocean of time. 

 For a much longer series of years than that during which man has 

 already occupied this world, the existence of the present state of in- 

 organic nature favourable to the duration of man seems to be secured, 

 so that for ourselves and for long generations after us, we have 

 nothing to fear. But the same forces of air and water, and of the 

 volcanic interior, which produced former geological revolutions, and 

 buried one series of living forms after another, act still upon the 

 earth's crust. They more probably will bring about the last day of 

 the human race than those distant cosmical alterations of which we 

 have spoken, and perhaps force us to make way for new and more 

 complete living forms, as the lizards and the mammoth have given 

 place to us and our fellow-creatures which now exist. 



Thus the thread which was spun in darkness by those who sought a 



