70 THE RECORD. 



stratified, or occurring in layers, like the silt of lakes and 

 seas, and undoubtedly the results of sedimentary or aqueous 

 operations. Between these two great forces the aqueous 

 and igneous the crust of the earth is ever held in habit- 

 able equipoise and never-ending variety of superficial aspect. 

 As the former tends to waste and wear down, and carry the 

 eroded material to the bottoms of lakes and estuaries, there 

 to be spread out in layers of varied consistency, so the 

 latter as incessantly strives to elevate and reconstruct 

 here throwing up the sea-bed into new islands, there dis- 

 rupting and undulating the solid crust, and anon casting 

 forth from volcanic craters new rocks and rocky compounds. 

 These forces being incessantly active, such transpositions of 

 sea and land must have frequently taken place piling the 

 newer deposits over those of earlier dates, varying it every 

 turn the relative distribution of sea and land, and offering 

 different conditions of life to plants and animals at each 

 successive mutation. And as the sediments of existing 

 lakes and seas envelop the remains of plants and animals 

 that have lived in their waters, or been borne thither by 

 floods and rivers, so also must there have been entombed in 

 the sediments of former epochs the plants and animals of 

 the period the deepest being the oldest or first-formed, 

 and the others occurring above them in order of time or 

 superposition. This is the great key to geological sequence : 

 the deeper, the older, and the older, the wider the dif- 

 ference between fossil plants and animals and those now 

 existing. To the paleontologist this physiological differ- 

 ence becomes, as it were, the measure of chronological pro- 

 gress ; stratigraphical sequence and vital gradation are but 

 convertible terms ; and either were resolvable into TIME 

 could we only determine the ratio of its increment and ad- 

 vancement. 



Presuming on the uniformity of nature's operations and 



