rr. 



It 



■-\ 



Ph> . 



% 



•7N, 



'Of 



re 





"^ qiestio 







thes 



», 





f 



* 



"ffianence of 

 iisite fcir tk 

 ■-"'^v the k 



dnea, nor li 



(v^ral reef in 



r 



gome part; 

 ..withea!" 



tie reef- 

 jecfions 



ar 



lose 



;terv over 



v,>.* 



of 



lit** 



Ch. XLIX.] 



LIME WHENCE DEEIVED. 



609 



He 



animals 



in the ancient ocean, 

 of the operations of animals, 'the quantity of calcareous 

 earth deposited in the form of mud or stone is always in- 

 creasing ; and that as a secondary series far exceeds the pri- 



may 



may 



portion of its calcareous strata.' 



lime 



rocks insisted upon in the passage here cited, was chiefly 

 deduced from observations on the geology of Scotland, with 



which i)r. MaccuUoch was familiar. Of late years our Cana- 

 dian surveyors have taught us that the most ancient series 

 of rocks yet discovered in the earth's crust, the Laurentian, 

 may contain vast formations of limestone, and one of these 

 is characterised by the Eozoon Canadense, a species of fora- 

 minifera. 



If Dr. Macculloch's propositions went no farther than to 

 suggest that every particle of lime that now enters into the 

 crust of the globe may possibly in its turn have been sub- 

 servient to the purposes of life, by entering into the com- 

 position of organised bodies, I should not deem the speculation 

 improbable ; but, when it is hinted that lime may be an 

 animal product combined by the powers of vitality from some 

 simple elements, I can discover no sufficient grounds for such 

 an hypothesis, and many facts militate against it. 



made in almost 



r 



become 



titles. 



almost 



But if no calcareous matter be supplied by waters 

 flowmg from the surrounding high grounds, or by springs, no 

 tufa^ or shell-marl is formed. The thin shells of one gen- 

 eration of mollusks decompose, so that their elements afford 

 nutrmient to the succeeding races ; and it is only where a 

 stream enters a lake, which may introduce a fresh supply of 

 calcareous matter, or where the lake is fed by springs, that 

 shells accumulate and form marl. 



AH the lakes in Forfarshire which have produced deposits 

 of shell-marl have been the sites of springs, which still evolve 



VOL. II. 



E E 



