MINERALOGY, 271 



furnaces decay, and at laft produce vegetables, 

 which cannot be afcribed to a black mould alone 

 carried thither by the wind. The fame may per- 

 haps happen with the natural flags in the open air.; 

 but we do not know if it is ib, nor what different 

 forms this and every other earth which circulates 

 in animals and vegetables further affumes : How- 

 ever, in fuch circumflances, as their particles be- 

 come or are already very minute, and mofl part of 

 the phlogiflon. becomes volatile, when acted upon 

 by heat or fire, it feems probable, that, by a flow, 

 feparation of the phlogiflon, or a union by means 

 of faks, this earth is mofl apt to become a clay, 

 provided it is not by any previous revolution laid 

 in fuch places as to change it into flate, pit-coal, 

 &c 



If at any time it mould happen that a volcano 

 mould burfl'out of a mountain, "whofe flrata we 

 knew before, we could at leaft imagine fome rea- 

 fons for this wonderful effect : However, the learned 

 would neverthelefs, perhaps, want fome knowledge 

 about the fubflances of the flrata, and the manner 

 of their formation -, fince in this circumflance water 

 and other obftacks have hindered people too much 

 from making the due obfervations thereon. 



Meanwhile, the more we confider, on the one 

 part, all the modifications and alterations the earths 

 undergo by means of fire and water, by the free 

 or impeded accefs of the air, by the volatility and 

 attraction cf the acid falts, whereby are pro- 

 duced foiution and hardening, compofition and 

 feparation •, and, on the other part, reflect on the 

 fhortnefs of a man's life, perhaps alfo dedicated to 

 other bufinefsj on the difficulty of obferving the 

 fubterraneous effe&s, and on feveral other things* 

 which prevent the making difcoveries, by which 

 we might find out fome eafier means to attain true 



knowledge 



