Affinities of Earths. 17 



fconfiftent with opacity, as this may arife from 

 a mere mechanical arrangement of the parts, 

 or the interpofnion of fome that are not 

 chymically combined, too great thicknefs* 

 &c. 



3 d - Cryftdlization. This proves that the 

 parts of the chryftalized fubftances have 

 been at fome period very minutely divided ; 

 and in general that they have been chymical- 

 ly combined with the menftruum, in which 

 they chryftallized ; though I agree with Mr. 

 Bergman that a chymical union with fuch a 

 menftruum is not always requiiite; but it 

 does not prove that they were chymically 

 combined with any other fubftanee which 

 chryftallizes with them, except fome other 

 mark of fuch union appears, and particularly 

 a denfny greater than could be expected from 

 the proportion and denfity of the component 

 parts. 



4 th - A more difficult Solubility in their com- 

 mon menftruums, and of courfe a ftill greater 

 difficulty of folution in menftruums, that acT: 

 only on one of the component parts. Of 

 this there are numberlefs indances, yet there 

 is one exception, viz. where one of the com- 

 ponent parts is reiblvable by the action of 

 the menftruum into an elaftic fluid, which 

 by its eruption fo powerfully agitates and 



G divides 



