THE S C EN JURY OF THE COAL P Eli I OH. 161 



them. Not only was there never another period of the 

 world when the supply of carbon was so great, but never, 

 before or after, were those frequent and gentle oscillations 

 so long continued which were the agencies in burying the 

 successive crops of vegetable growths. At least, such fre- 

 quent oscillations never before or since occurred at a time 

 when the level of the continents so nearly coincided with 

 the level of the sea. And, lastly, these very oscillations, 

 while they were subserving this collateral end — which was 

 still important enough to have been the sole and ultimate 

 end — were only the symptoms of a great continental prep- 

 aration, which was going on from the region of the At- 

 lantic to that of the Pacific shores, and which had been in 

 progress, and attended by similar, though much less fre- 

 quent oscillations, from that remote period when the 

 shrinking of the molten nucleus of the world located those 

 huge wrinkles in the stiffening crust which were to be aft- 

 erward deepened into the beds of the two great oceans. 

 Verily, here is a scope and comprehensiveness of plan 

 which must command our highest admiration. 



The same general preparatory movements were still to 

 be continued — continued till the finished earth had been 

 elaborated for the reception of man. It would seem that 

 the frequent oscillations of the Coal Period were but the 

 tremblings of the strained crust, pushed to the very verge 

 of violent rupture by the two enormous masses of water. 

 i:>y turns, the central areas had been protruded above the 

 waves, and by turns the tension had found relief, and the 

 uplifted crust dropped back for a time to its submarine 

 horizon. Not before the collateral uses of these phenom- 

 ena had been subserved did the tension of the crust reach 

 the measure of a grand upheaval. After trembling for 

 ages beneath the immense and increasing pressures of two 

 great oceans, it burst up in enormous folds thousands of 



