MODE OP OPERATION OF CALX AS MANURE. 95 



matter, which, I suppose, must be chemically combined with the 

 calcareous earth, and by that means only is preserved from the 

 putrefaction and waste that would otherwise certainly and speedily 

 take place. Indeed, the large proportion of animal matter which 

 thus helps to constitute some kinds of shells, instead of making 

 them more perishable, serves to increase their firmness and solidity. 

 When long exposure, as in fossil shells, has destroyed all animal 

 matter, the texture of the calcareous substance is greatly weakened. 

 A simple experiment will serve to separate, and make manifest to 

 the eye, the animal matter which is thus combined with and pre- 

 served by the calcareous earth. If a fresh-water mussel-shell is 

 kept for some days immersed in a weak mixture of muriatic acid 

 and water, all the calcareous part will be gradually dissolved, 

 leaving the animal matter so entire, as to appear still to be a whole 

 shell but which, when lifted from the fluid which supports it, 

 will prove to be entirely a flaccid, gelatinous, and putrescent sub- 

 stance, without a particle of calcareous matter being left. Yet 

 this substance, which is so highly putrescent when alone, would 

 have been preserved in combination with calcareous matter, in the 

 shell, for many years, if exposed to the usual changes of air and 

 moisture ; and if secured from such changes, would be almost im- 

 perishable. 1835.] 



Calcareous earth has power to preserve those animal matters 

 which are most liable to waste, and which give to the sense of 

 smell full evidence when they are escaping. Of this, a striking 

 example is furnished by an experiment which was made with care 

 and attention. The carcase of a cow, that was killed by accident 

 in May, was laid on the surface of the earth, and covered with 

 about seventy bushels of finely divided fossil shells and earth 

 (mostly silicious), their proportions being as thirty-six of calcare- 

 ous, to sixty -four of silicious earth. After the rains had settled 

 the heap, it was only six inches thick over the highest part of the 

 carcass. The process of putrefaction was so slow, that several 

 weeks passed before it was over ; nor was it ever so violent as to 

 throw off any effluvia that the calcareous earth did not intercept 

 in its escape, so that no offensive smell was ever perceived. In 

 October, the whole heap was carried out and applied to one-sixth 

 of an acre of wheat and the effect produced far exceeded that of 

 the like calcareous manure alone, which was applied at the same 

 rate on the surrounding land. No such power as this experiment 

 indicated (and which I have since repeated in various modes, and 

 always with like results), will-be obtained, or expected, from using 

 clay as the covering earth. 



Quick-lime is used to prevent the escape of offensive effluvia 

 from animal matter ; but its operation is entirely different from 

 that of calcareous earth. The former effects its object by " eating" 



