15-2 UK ETCHES OF CREATION. 



solve the problem of the elimination of the noxious gas 

 which unfitted the atmosphere for respiration. Till this 

 was done the progressive series of animal forms must here 

 be arrested, and the last term of the series, man, toward 

 which all the steps of the previous preparation had con- 

 verged, must remain a distant and unattainable hope, and 

 Nature fail of her completeness and her crown. 



The development history of the American continent had 

 been conducted through a succession of vertical oscilla- 

 tions, extending eastward to the still subaqueous ridges of 

 the Appalachians, and westward to the corresponding nas- 

 cent ridges of the Pacific slope. The valleys of the two 

 great oceans had been continually deepening beneath the 

 pressure of the superincumbent masses of waters, and, as a 

 consequence, the intervening continental space had suffered 

 a corresponding vertical uplift, so that the waters had 

 been poured off from the site of the future continent, and 

 a mere shallow lagoon occupied the present area of the 

 Middle and Southern States and Territories. The oscilla- 

 tions of the submarine soil down to the dawn of the period 

 now under consideration — sometimes increasing and some- 

 times diminishing the depth of the waters — left it at last 

 but little sunken beneath the general surface of the sea. 

 [See the areas marked C, Fig. 58.] 



Now a state of more than usual uneasiness began to 

 manifest itself. The ocean bed heaved and sank as in the 

 breathings of a mortal agony. Surges mountain -high 

 rolled up the sterile strand, and, wasted with their own 

 violence, fell back upon their ocean couch. This, of course, 

 was not the period for an abundance of animal life. But, 

 if the usual fecundity of Nature was for a time suspended 

 on our continent, some other continent may have been the 

 theatre of its display. In America the crumbling margins 

 of the sea were worked up into cubic miles of sand and 



