34.3 ACTION OF HEAT. 



i'ome of ihe firft of ihefe experiments, I loofened the cradle, by 

 plunging the barrel into iiealed brine, or a ftrong folution ot 

 muriate of lime; which lafl: bears a temperature of 250^ of 

 Fahrenheit before it boils. For this purpofe, I ufed a pan 

 three inches in diameter, and three feet deep, having a Hat 

 bafon at top to receive the liquid when it boiled over. The 

 metliod anfvvered, but was troublefome, and I laid it afide. 

 I have had occafion, lately, however, to refume it in fome 

 experiments in which it was of confequence to open the 

 barrel with the lead poffible heat*. 



By Ihefe methods I made a great number of experiments, 



with refults that were highly interefting in that ftage of the 



bufmefs, though their importance is fomucb diminithed by the 



fubfequent progrefs of the inveftigalion, that I think it proper 



to mention but very few of them. 



Calcareous fpar On the 31ft of March, ISOl, I rammed forty grains of 



ha'rTdenfe'"^" P^un^'ed chalk into a tube of green bottle-glafs, and placed it 



marble by heat in the cradle as above defcribed. A pyrometer in the mufHe 



of 2^" Wedg- jjfQ, ^i^^ jj,g barrel indicated 53°. The barrel was expoled 



wocj. . . . . 



to heat during feventeen or eighteen minutes. On withdraw- 

 ing the cradle, the carbonate was found in one folid mafs, 

 which had vifibty flirunk in bulk, the fpace thus left within 

 the tube being accurately filled with metal, which plated the 

 carbonate all over without penetrating it in the leaft, fo that 

 l!:e metal was ealily removed. The weight was reduced 

 from forty to thirty-fix grains. The fubftance was very hard, 

 and relifted the knife better than any refult of the kind pre- 

 vioufly obtained ; its frailure was cryftaliine, bearing a re- 

 femblance to white faline marble; and its thin edges had a 

 decided femitranfparency, a circumftance firft obferved in this 

 refult. 

 Calcareous fpar On the 3d of March of the fame year, I made a {imilar 

 jenderedciyftal. gj^pg^jjjjgjj{^ j,^ which a pyromeler-piecc was placed within 



boidal fraifture . _ -,-,,. . , , /• i • i 



I }jg ,j 23«'. * In many of the followmg experiments, lead was ufed in place 



of the fufible metal, and often with fucceis ; but I loft many good 

 jefults in this way : for the heat required to liquefy the lead ap- 

 proaches fo near to rednefs, that it is difficult to difengage the 

 cradle without applying a temperature by which the carbonate is 

 injured. 1 have found it anifwer well, to furround the cradle and a 

 few inches of the rod with fufible metal, and to fill the reft of the 

 barrel with lead. 



the 



