[9 I 



earth thus feparated ftvould be more refradlory than before, 

 fliould be alfo expedled ; both becaufe it is not repulverized 

 (at leaft not ftated to have been fo) and becaufe much of the 

 alkali, which is its. menftruum, evaporates and is volatilized during 

 the flow refrigeration. But if the heat applied be much greater 

 than at firft, it may be vitrified a fecond time, as more of moft 

 falts may be diffolved in a fmall quantity of water at 212^ 

 than at 150". 



But to reproduce granite from a general fufion of all its in- 

 gredients by a refrigeration ever fo flow, is a very different cafe 

 from that we have jufl: considered. 



Granite is an aggregate ftone confifting of quartz, felfpar 

 and mica ; of thefe the mod fufible is undoubtedly the felfpar, 

 and the quartz the leaft ; let us then to indulge the worthy 

 Baronet fuppofe all three in perfeifl fufion in a high degree of 

 heat, and afterwards flowiy cooled, and thus each (though vouched 

 by no experiment! gradually reproduced ; the quartz, with the 

 exception of the proportion thereof which enters into the com- 

 poiition of felfpar and of the mica would undoubtedly cryflallize 

 firft on the fmalleft diminution of heat, and, being congealed in 

 a medium ftill in a liquid ftate, I do not fee why it fhould not 

 form legular cryftals, which neverthelefs fcarce ever occur in 

 gra lite except in cavities. Over this, and after a confiderable ' 

 interval of time, the mica fhould alfo be regularly cryftallized, 



Vol. VIII. B . and 



