THE CHAIN OF LH'E TRACED I5ACKWARU 



5 



axis is diminishing in rapidity. In summing up 

 these and other changes, Lord Kelvin says : " To 

 hold the doctrine of the eternity of the universe 

 would be to maintain a stupendous miracle, and one 

 contrary to the fundamental laws of matter and 

 force." 



So, on our earth itself, we can now assign to their 

 relative ages those great mountain chains which 

 have been emblems of eternity. We can transfer 

 ourselves in imagination back to a time when man 

 and his companion animals of to-day did not exist, 

 when our continents and seas had not assumed their 

 present forms, and even when the earth was an 

 incandescent mass with all its volatile materials 

 suspended in its atmosphere. It is true that in 

 all the changes which our earth has undergone the 

 same properties of matter and the same natural laws 

 have prevailed ; but the interactions of these pro- 

 perties and laws have been tending to continuous 

 changes in definite directions, and not infrequently 

 to accumulations of tension leading to paroxysmal 

 vicissitudes. 



If all this is true of the earth itself, it is especially 

 applicable to its living inhabitants. Successive 

 dynasties of animals and plants have occupied 



