or f^otmction of IFfrtaefo 1 1 



eafily believe, their Aggregate will 

 prove too heavy or unwieldy for a- 

 volation. And to fhew^ that the fire 

 may effeft a J^vigation in the furfa- 

 ces of fbme corpufcles, I have fome- 

 times caufed Minium^ and fome o- 

 ther calces s that I judged convenient, 

 to be melted for a competent time, 

 in a vehement fire conveniently ad- 

 tnioiftred} whereby, according to 

 expectation^ that which was before 

 a dull and incoherent powder, was 

 reduced into much grofler corpufcles, 

 multitudes of whofe grains appea- 

 red fmooth, glittering, and almoft 

 fpecular, like thofe of fine litharge 

 of gold J and the maffes that thefe 

 grains compofed, were ufualiy folld 

 enough and of difficult fufion. And 

 when we make glafs of Lead per fe % 

 (which I elfewhere teach you how 

 to doe,) 'tis plain, that the particles 

 of the Lead are reduced to a great 

 fmoothnefs 5 fince, wherefoeveryou 

 break the glafs., the furfaces, produ- 

 ced at the crack, will not be jagged, 

 tut fsnoothj and confiderably ipecu- 



lar. 



