442 



Miscellaneous. 



But we have now nearly approached the termination of the secondary 

 period, for the paucity of terrestrial plants and animals in the cretace- 

 ous series and greensand does not tempt us to linger long amidst their 

 oceanic deposits. But to the chemist it seems strange from whence 

 came those vast deposits of carbonate of lime in the cretaceous beds. 

 The plants are not numerous, and almost entirely marine; yet from 

 the quantity of pyrites which occurs, it is apparent vast quantities of 

 organic matter must have been in decay. 



The perishable nature of marine plants prevents them being accumu- 

 lated in very large quantity. Hence we might still conceive, that the 

 ocean was covered with marine plants at this period, which by their 

 decay might so furnish carbonic acid as to decompose the sulphate of 

 lime existing in the sea water, and thus occasion the deposition of car- 

 bonate of lime ; thus the atmosphere would be robbed of large quanti- 

 ties of carbonic acid. But the magnitude of such deposits astonish us, 

 and would compel us to relinquish this, even as a partial cause, did we 

 not, on the other hand, consider the great extent of geological epochs. 



Now comes the close of the secondary period. We have glanced at 

 the nature of its organic remains, from the silurian rocks to the green- 

 sand; we have been struck with the development of organic life; we 

 found it partly owing to the physical conditions and positions of land 

 and sea — and with these we had nothing to do ; — but we found it also 

 dependent on the chemical constitution of the atmosphere ; and that 

 when vegetation gradually purified the air from its noxious ingredients, 

 other forms of animal life sprung into existence. When traversing these 

 lands of former times, it is difficult for us to conceive that we are exa- 

 mining our own world. The striking progression of organic life must 

 have been due to some cause. Why, may I ask the followers of Lyell, 

 who believe that organic beings may have existed long before the pri- 

 mary periods, although their remains have been destroyed by heat — why 

 this progression of animal life? And, wherefore, may I ask the followers 

 of Daubeny, did land animals not sport in the forests of the carboni- 

 ferous land? No mighty operations of nature then acted as antago- 

 nists to their existence ; the climate must have been congenial ; 

 the war of the elements not greater, if so great as now. And 

 wherefore, when in the course of ages, those forests become en- 

 tombed, did land animals then start into being? Can these, or 

 many similar questions be replied to, without admitting some changes 

 in the states of the medium in which both plants and animals exist, 

 or can the uniform progression of animal life be attributed to 

 entirely local or adventitious causes ? Let us not contort the face 



