40 Natural Histoiy of Molluscous A?iimals : — 



a very little lime, or perhaps none at all. If you ask me how 

 this can be, I can only answer that it is one of the wonderful 

 and inexplicable effects of a living principle. But the fact 

 being as I have stated, you will readily grant that such a gift 

 was not likely to be bestowed for a minor purpose ; and though 

 we cannot unfold all the uses of this metamorphosis of matter, 

 yet we know enough to prove its vast importance. " Chalk, 

 marl, and limestone,'^ says BufFon, " consist entirely of the 

 dust or fragments of shells," * This, at first, may seem an 

 extravagant doctrine, and Imagination herself startles when 

 she attempts to sum up the millions and tens of millions which 

 must have gone to the formation of such deep and extensive 

 strata. It is nevertheless, in a great measure, true f ; and, as 

 a proof of it, I will have pleasure in showing you, when next 

 you visit me, strata of limestone, some miles in extent, and 

 many feet deep, composed almost wholly of shells, thousands 

 of which are so well preserved, that you may give them a 

 " local habitation and a name " in the systems of naturalists. 

 Cast a glance at your marble chimney-piece, and you will, in 

 all probabiHty, trace therein the figures of shells that have 

 been, not the sportive freaks of the formative powers of nature, 

 as philosophers once believed, but the true remains of living 

 creatures which " have put off flesh and blood, and are be- 

 come immutable." Hence it is that the study of shells, so 

 long ridiculed by the wits of the age, as an abuse of time and 

 waste of money, becomes so important, or rather necessary, to 

 all those who make the structure of the earth, and the various 

 changes which it has undergone, an object of attention, " For 

 shells are found in abundance in a great variety of rocks and 

 positions : they constitute the medals of the ancient world ; 

 and, from an accurate acquaintance with their different spe- 

 cies, and with the nature of the animals that inhabited them, 

 many curious and important deductions respecting the form- 

 ation and changes of the crust of the earth may be drawn." f 

 It is from their composition that even recent shells become 

 useful as a manure, a purpose to which they are occasionally 

 applied in this and other countries ; and it has been ascer- 

 tained by comparative experiments, that, on turf lands in par- 



* Nat. Hist., vol. i. p. 214. j also vol. u. p. 221., &c. The word shell is, 

 however, used here in a very extensive sense, so as to include corals, madre- 

 pores, Echlniy &c. ; still it does not materially affect the text. 



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

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

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

 face of the globe, have resulted from the decomposition of animal matter 

 deposited during a series of ages." See his Travels, vol. i. p. 624 — 26. 4to. 



X Thomson's Hist, of the Royal Society, p. 83. 



