I^OdJ EFFECTS OP HEAT. 



Other fpecimens thefe few days. When employed in examining tliefe refults, 



pofed to heat ^ ™*^^ ^^ ^^^ Carbonate broke in two, and exhibited the frac- 



under ftrong tare now before us nearly in as good a ftate as it was originally. 



preffure. j immediately inclofed it in a glafs tube, and fealed it up with 



' wax, fo that I have hopes of preferving it. In the mean time 



I am happy tofliew it entire to the Society. No. 18, likewife 



from pounded chalk is perfedly frefh and entire, though made 



more than a year ago; it thews fome beautiful clear cryftals of 



fpar in parallel plates, but is fo fmall as to require the ufe of a 



glafs. 



Nos. 19, 20, 21, fliew examples of fufion and a6tion on the 

 tubes. In number 19, a fhell is finely united to fome pounded 

 chalk. In No. 20, the mafs originally of pounded chalk is 

 iinking upon itfelf, and afting at the fame time upon the tube. 

 The pure carbonate in its fiadiire (liewing brilliant facettes of 

 cryftallization. In No. 21, the carbonate in a ftate like the 

 laft; the compound of porcelain and carbonate fliewing its li- 

 quidity by penetrating the tube fo as to form a diftind vein, 

 and then fpreading on its outfide to a confiderable extent, teri" 

 minating with the black line above alluded to. 



Nos. 22i 23, 24, give proofs of entire fufion. In No. 22, 

 we fee two porcelain tubes inclofed for prefervation in a glafs 

 tube, the fealed end of which muft be held downwards, to 

 Ihew the pofition in which the experiment was made. The 

 innermoft porcelain tube ftands with its muzzle upwards, and 

 the outermoft covers it in the inverfe pofition ; the carbonate 

 was contained in the inner tube. During the aftion of heat, 

 the barrel failed fuddenly, and the carbonate has boiled over 

 the lips of the inner tube, running down, as here appears, 

 almoft to its bottom ; thus proving that immediately previous 

 to the failure of the apparatus, the carbonate had been in a 

 liquid ftate. No. 23, two mafles of carbonate, welded toge- 

 ther in a complete ftate of froth. The fubftance fliining and 

 tranfparent. No. 24-, two feparate maffes expofed together to 

 heat; one from pounded chalk, now in a ftate quite like the 

 laft; the other put in as a lump of chalk dreflfed flat at both 

 ends, and a letter cut on each end (as done in many of the 

 experiments.) It is in a thining and almoft tranfparent ftate; 

 at one end the flat form and the letter are ftill vifibie; the other 

 end is completely rounded in fufion, with a glofly ftrrface. 



Nos. 



