4 PRINCIPLES OF PALAEONTOLOGY. 



undergone changes of such magnitude as to render it seemingly 

 irrational to suppose that they could have been produced by 

 any process now in existence. If we add to the above the 

 prevalent belief of the time as to the comparative brevity of 

 the period which had elapsed since the birth of the globe, we 

 can readily understand the general acceptance of some form of 

 catastrophism amongst the earlier geologists. 



As regards its general sense and substance, the doctrine of 

 catastrophism held that the history of the earth, since first it 

 emerged from the primitive chaos, had been one of periods of 

 repose, alternating with catastrophes and cataclysms of a more 

 or less violent character. The periods of tranquiUity were sup- 

 posed to have been long and protracted ; and during each of 

 them it was thought that one of the great geological "forma- 

 tions " was deposited. In each of these periods, therefore, the 

 condition of the earth was supposed to be much the same as it 

 is now — sediment was quietly accumulated at the bottom of the 

 sea, and animals and plants flourished uninterruptedly in suc- 

 cessive generations. Each period of tranquillity, however, was 

 believed to have been, sooner or later, put an end to by a 

 sudden and awful convulsion of nature, ushering in a brief and 

 paroxysmal period, in which the great physical forces were 

 unchained and permitted to spring into a portentous activity. 

 The forces of subterranean fire, with their concomitant pheno- 

 mena of earthquake and volcano, were chiefly refied upon as 

 the efficient causes of these periods of spasm and revolution. 

 Enormous elevations of portions of the earth's crust were thus 

 believed to be produced, accompanied by corresponding and 

 equally gigantic depressions of other portions. In this way 

 new ranges of mountains were produced, and previously exist- 

 ing ranges levelled with the ground, seas were converted into 

 dryland, and continents buried beneath the ocean — catastrophe 

 following catastrophe, till the earth was rendered uninhabitable, 

 and its races of animals and plants were extinguished, never to 

 reappear in the same form. Finally, it was believed that this 

 feverish activity ultimately died out, and that the ancient peace 

 once more came to reign upon the earth. As the abnormal 

 throes and convulsions began to be relieved, the dry land and 

 sea once more resumed their relations of stability, the condi- 

 tions of life were once more established, and new races of ani- 

 mals and plants sprang into existence, to last until the super- 

 vention of another fever-fit. 



Such is the past history of the globe, as sketched for us, in 

 alternating scenes of fruitful peace and revolutionary destruc- 

 tion, by the earlier geologists. As before said, we cannot 



