THEIR CREATION AND SUCCESSION. 91 



as Linnaeus and many geologists have maintained, * the con- 

 el usion that carbonate of lime is formed in the body of the 

 mollusks, independent of all exterior source, would neces- 

 sarily flow from the axiom ; but the opinion has been con- 

 tested of late, and, indeed, rendered untenable. Still it 

 seems to be almost demonstrable that extensive deep calca- 

 reous strata which exist in different parts of the world, have 

 originated from the detritus or decomposition of shells ; 

 and when we take into consideration the great extent of 

 these formations, and the prodigious quantity of lime which 

 enters into them, we are drawai to coincide with Dr. Bostock, 

 one of the best and most cautious physiologists of the age, 

 that the opinion of its having been a mere excretion of 

 matter which had passed through the system, though it ac- 

 cords best with our ideas of the usual operations of nature, 

 " is rendered improbable from the immense quantity of 

 matter which the animals must have appropriated to them- 

 selves ; and it is not very easy to conceive in what state the 

 lime could have existed previous to its reception into their 

 system." -f 



In whichever way we decide this interesting question, 

 whether the testaceous mollusca merely excrete and recon- 

 solidate the dissolved lime, or have the power of forming it 

 from materials in which our chemistry has hitherto detected 

 none, it little affects our estimate of their influence in the 

 construction of the globe. Called into life at an early period 

 of the w^orld's age, among the first indeed of living beings 

 which broke the dead rest and stillness of its infancy, they 

 immediately began their appointed work, and multiplying in 

 myriads which no numbers can reckon up, their shells be- 

 came the foundation, and if not the chief, certainly a very 

 material part of enormous strata and chains of rocks ; nor 

 have they ceased, through all the intermediate ages, to play 

 a preponderating part in every revolution which has occurred. 

 In the earliest fossiliferous rocks we find buried the remains 

 of vast numbers of brachiopods (which appear, indeed, to 

 have been the principal tenants of that primaeval sea), of 



* " If Saussure," says Dr. Clarke, " had not discovered limestone lying 

 beneath rocks of the most ancient formation, the French wonld long ago 

 have established a theory that all the strata of carbonated lime, upon the 

 surface of the globe, have resulted from the decomposition of ainmal matter 

 deposited during a series of ages." — Travels, i. 624 — 626. 4to. — See also 

 Macculloch's Geology, ii. 414; and the article "Organic Kcmains" in 

 Brewster's Edinb. Eiicyclop. xv. 705, 706. 



t Syst. of Physiology, ii. 384— and particularly the note at p. 386. See 

 also Thomson's Hist. Roy. Society, 211, 212. De La Beche's Gcog. 

 Manual, 452, 453. 



