64 EXPERIMENTS on WHINSTONE and LAVA. 



ftream on three different days. It was in general concealed by 

 a thin white fmoke, which the wind blew alide occanonally, 

 fo that I could diftinclly fee the lava as it burfl: from the fide of 

 the hill. It was then of a bright white heat, and flowed with 

 the agility and rapidity of water, in all refpects refembling melt- 

 ed iron running from the furnace. The liquid, at its firft emer- 

 gence, manifefted a ftrong effervefcence, which fubfiding as the 

 heat abated, iliewed itfelf at laft only in the burfting of fome 

 very large bubbles, accompanied with a white fmoke. Where 

 I approached the ftream, it was ftill of a ftrong red heat, and 

 had the confidence of honey. I thruft a ftick into it with 

 eafe, to the end of which fome of the lava adhering, by its 

 vifcidity, allowed itfelf to be drawn out into threads, and was 

 found, when cold, to have a mining furface, and a vitreous 

 fracture. 



Being thus convinced that I had met with a lava of glafs, I 

 prepared fome moulds of flucco, in which I meant to take cafts 

 with that rare fubftance ; and with this view returned to 

 the mountain. I found the ftream was not fo liquid as at firft, 

 but I was able, by means of a ladle fixed on the end of a pole, 

 to lift the fpecimen now before us in a ftate like dough. I 

 then preffed it with a feal, by which means, though too coarfe 

 to receive an accurate imprefuon, it took the fhape it now 

 bears, which is that of the ladle. It is very porous, one- 

 third of it nearly being occupied by air holes. It contains a 

 great number of fmall white cryftals of Vefuvian garnet, em- 

 bedded in a black fubftance, which completely refembles the 

 glafs obtained in our experiments from lava by rapid cooling 

 after fufion. Befides all their other properties, it pofTeffes the 

 fufibility of the glafTes, iince it foftens completely at 1 8, that is, 

 14 or 15 degrees below the foftening point of any of the ftony 

 lavas. Being expofed to the procefs of regulated cooling, it 

 gave the fame refult as all the other lava glafTes. In the lower 



points 



