Prof. Helmholtz on the Interaction of Natural Forces. 515 



also speaks not so much for the climate of the country as for 

 the throats of the German drinkers. 



But even though the force store of our planetary system is so 

 immensely great, that by the incessant emission which has oc- 

 curred during the period of human history it has not been sen- 

 sibly diminished, even though the length of the time which must 

 flow by, before a sensible change in the state of our planetary 

 system occurs, is totally incapable of measurement, still the 

 inexorable laws of mechanics indicate that this store of force, 

 which can only suffer loss and not gain, must be finally ex- 

 hausted. Shall we ten-ify ourselves by this thought ? Men 

 are in the habit of measuring the greatness and the wisdom of 

 the universe by the duration and the profit which it promises to 

 their own race ; but the past history of the earth already shows 

 what an insignificant moment the duration of the existence of 

 our race upon it constitutes. A Nineveh vessel, a Eoman 

 sword awakes in us the conception of grey antiquity. What 

 the museums of Europe show us of the remains of Egypt and 

 Assyria M^e 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 pyi-amids or 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 com- 

 parison 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 ? Dif- 

 ferent 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 com- 

 pare it with the ages during which the world was a ball of fused 

 rocks. For the duration of its cooling from 2000° to 200° Cen- 

 tigrade, the exporiments 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 

 history 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 occujiied this world, the existence of the 

 present state of inorganic nature favourable to the duration of 

 man seems to be secured, so that for ourselves and for long 



