PHYSICAL AND LITERARY. 17 



Jour from white changed to grey or afliy. 

 When water was poured upon this cal- 

 cined fubftance, many air-bubbles roie to 

 the furfp/te with a biffing noife, and as 

 flrong lime-water v^ras in a fliorttime pro-' 

 duced as I had ever obtained from any 

 quick -lime. 



The calcination of the powders extract' 

 ed from the other marles was attended, in 

 every circumftance, with the fame fuccefs; 

 that from fliell-marle not excepted. 



FrOxM thefe experiments, I think, the 

 nature of marie is fufficiently evident*. 



Vol. III. C Marie 



• Here it may be afked, if fuch is the compofition of 

 all earth-marles, whence comes it, that foanc earths of 

 that kind, or what flrongly refembles them, are fo dc- 

 ftruftive to the growth of vegetables ? In anfwcr to this, 

 it muft be remarked, that many i'offils, differing widely 

 in their nature from marie, have frequently, fromrefpm- 

 blance, been employed as marie, iimong the Icffils of 

 this country, is oft-times found a fpecies of the Pyrites, 

 Lapis atrametJtofus of Cramer, which in colour nearly 

 refembles fome of the earth-marles. I have feen a bed 

 of this which contained a confidcrable proportion of 

 calcarious earth. It may occur among beds of marie ; 

 but, whenever it is employed in agricukyre, its eSt&s 

 jDXi&. be unfavourable* 



