&4 OBSERVATIONS 



is true indeed that there are many of thefe angles obtufe ; but 

 there are an equal number, which are as much lefs than the 

 right angle, as the others are greater. * 



In whichfoever of thefe two lights we are to take the explana- 

 tion of this mineral appearance, my argument, viz. that thefe 

 two fubftances had concreted together from a fluid (late of fu- 

 sion, is equally fupported. For whether cryftalizing quartz 

 fhall inclofe a body of feld-fpar, or concreting feld-fpar deter- 

 mine the lhape of fluid quartz ; particularly, if we have, as is 

 here alfo the cafe, two folid bodies mutually including and in- 

 cluded by each other, it amounts to a demonftration, that thofe 

 bodies had concreted from the fluid ftate of fufion, and had 

 not cryftalized in the manner of falts from a folution. There- 

 fore, here is the teftimony of granite from three different places 

 of the earth, viz. from the Daouri, from the Oural Mountains, 

 and from Scotland, by which this truth is manifefted. 



It would feem that the circumftances, neceffarily concurring 

 in order to produce this particular effect, are rarely to be found ', 

 and the external circumftances which attend it in the eaft, do 

 not appear to accompany it in the weft of Europe. In Scot- 

 land, this ftone neither forms the walls of a vein, nor are to- 

 pazes found connected with it, as M. Patrin found it in the 

 eaft. The internal circumftances, therefore, which, in the 

 mafs of granite, determine this particular conftruc'tion of the 

 rtone, are to us unknown. 



It is not, however, confined to any particular place orfituation; 

 it is found both at the level of the fea, and upon the higheft parts 

 of the earth, and in countries extremely diftantfrom each other. 

 Now, considering that nothing is more general in minerals than 

 granite, it is furprifing that this particular modification of its 

 conftituent parts has been fo little obferved. But, as it would 

 feem to take place only in fmall portions of the granite mafs, 

 there may be fimilar examples in many mafles, or in moft gra- 

 nite 



