314 Scientific Geology. 



Dr. Macculloch* leans to the affirmative : but another able geologist, 

 Mr. Lyell,f defends the negative. Mr. Lyell, however, does not object 

 to the idea that " every particle of lime that now enters into the crust 

 of the globe, may possibly in its turn have been subservient to the 

 purposes of life* by entering into the composition of organized bo- 

 dies;" but to the opinion that " lime may be an animal product com- 

 bined by the powers of vitality from some simple elements." Dr. 

 Macculloch thinks his views of the subject rendered probable, by the 

 great increase of calcareous strata the higher we rise in the series of 

 formations, and by the great extent of existing ,coral reefs. But Mr. 

 Lyell says that in ponds or lakes, which are not fed by springs con- 

 taining carbonate of lime in solution, there will be no accumulation 

 of shells producing tufa and shell marl ; one race of animals fur- 

 nishing by their decomposition only calcareous matter enough to sup- 

 ply the next generation ; and hence he infers that the animals do not 

 secrete lime. And he explains the greater quantity of calcareous 

 matter in the newer strata, by the constant transfer of this matter 

 from the inferior to the superior rocks by internal heat and springs. 



But however this point may be decided, it is certainly an inter- 

 esting thought that all existing limestone may have once formed a 

 part of organized beings. That much of it in the secondary rocks 

 did enter into the composition of animals, is obvious from the im- 

 mense quantity of their remains now found in such rocks. But why 

 are the primary rocks destitute of them ? Dr. Macculloch says that 

 he has found organic remains in one instance, "in a calcareous quartz 

 rock situated beneath gneiss." But he has also shown conclusively 

 that limestones full of organic remains, when in contact with trap, 

 are converted into highly crystalline masses, and the organic remains 

 entirely obliterated for a certain distance from the trap. Such a 

 change he supposes may have been undergone by all the primary 

 limestones. 



It is well known that calcareous soils are of all others most fertile. 

 Now if it be true that the quantity of limestone on the globe is in- 

 creasing, it will follow that there is a progressive increase of fertility. 

 Such a view would certainly accord 'with our ideas of the Divine 

 beneficence : but we should not forget the danger of hasty inferences 

 on such subjects. 



* System of Geology, vol. 1. p. 220. 



t Principles of Geology, vol. 2. p. 298. London, 1832. 



