THE PRIMEVAL AMERICAN CONTINENT. 231 



world be sunk and raised, preserving, possibly, througb all tlie changes 

 the rudimentary outlines of hills and valleys by which it was first 

 characterized and marked. And imagining that every new stratum 

 was ingeniously varied in the color and to some extent in the nat- 

 ure of its mineral constituents, and that, upon each reappearance of 

 this diminutive continent, the skillful experimentalist spread a new 

 form of life, what at last might be, after some exposure to weather- 

 ing and change, the character of its surface ? Evidently something 

 like this : in the first place, since, in consequence partly of denudation 

 and partly of only partial submergence, certain tracts will aj^pear 

 cleared of the later deposits, we will find numbers of the whole series 

 laid bare in spots from the highest point, where, as presupposed, only 

 the primitive layer is seen, to the outskirts of the island where the lat- 

 est layer forms the surface ; or to interior depressions, where lake-like 

 centers existed alternately filled and emptied with each recurring del- 

 uge. Endless diversity might be introduced into such a scheme, so far 

 as local detail is concerned, but under the conditions given the island 

 would exhibit lines of stratification, each distinguished by color or 

 fossils, and following each' other in the order instituted by the youth- 

 ful world-makers. Along the crevices and tiny gullies we might 

 detect the minute succession of various strata, and at intervals frag- 

 ments of the buried life would be revealed. Enlarge this minute 

 illustration till it assumes continental dimensions, reverse the periodic 

 inundations from the water rising to periodic inundations from the 

 land sinking, and in a rude way, subject to important modifications, 

 the reader will be prepared to realize the formative system developed 

 in the construction of our northern hemisphere. 



Through a sequence of phases, somewhat distinctively bounded by 

 periods of depression and consequent submergence, and periods of ele- 

 vation and consequent drainage, land was added to an initial nucleus by 

 enormous marine accumulations, the debris of animal organisms, and 

 the detritus from terrestrial abrasion. Chemical action, heat, and 

 molecular transference hardened these layers into stone, and thus the 

 new-made land, though undergoing change from recurring submer- 

 gence, and through subaerial denudation, yet, to a great extent, re- 

 sisted removal while it contributed to the growth of the incipient 

 continent, and formed the ground upon which new-laid strata were 

 heaped. 



In the American Museum of N'atural History, seven maps, the work 

 of Professor R. P. Whitfield, have recently been added to the Geologi- 

 cal Cabinet, intended to exhibit the growth of the eastern half of the 

 North American Continent from 95 west lonsfitude eastward to its 

 shores. The scheme of their arrangement is the exhibition, by con- 

 trasted colors, of the superficial areas where to-day the rocks of the 

 various geological epochs are exposed, beginning with the oldest and 

 rising to the youngest, whereby we seem to seize at critical points the 



