Zi ESSAYS AND OBSERVATIONS 



SECT. VII. 



THE two following Experiments werg 

 made with a view to difcover what change 

 the adion of fire produced upon the cal- 

 carious earth of marlCj with regard to its 

 folubility in acids* 



E X P E R. 



fnpport themfelves in their place without any afllilance? 

 from the calcarious earth. But, whea water is applied 

 tomarle in its natural ftate, it gradually makes its way 

 thro' the whole mafs, which it reduces to powder. This, 

 ihereRre, is a proof that the calcarious particles of naarle 

 have no mutual cohefion, fince the whole mafs moul- 

 t!ers down as foon as the cohefion of the clay is deftroy-* 

 ed. /^nd, as no acid can find admittance deeper thaa 

 the fufface, to dilTolve the calcarious earth in calcined 

 rtiarle, we may conclude, that taking out one particle ' 

 rf this earth does not open a paffage to another ; and 

 therefore,' that thefe particles lie in fep^race cells. Frona 

 *hat is here laid, we mjy plainly fee the neceffity of 

 pnlvtrization in Experiment 17. and 22. and likewife ho'.v 

 K happens, that when the clay, mixed wi'h a calcari- 

 rious earth, is below a certain proportion, the compofi- 

 tion, when burnt, cannot refift the influence of water. 

 It may be here aflced, how it happens, that acids can 

 ftad admittaBce to the calcarious earth of marles, even 



