MODIFIED by COMPRESSION. 101 



IV. 



Experiments in Gun- Barrels refumed. — The Vertical Apparatus applied 

 to them. — Barrels bored in /olid Bars. — Old Sable Iron. — Fufion of 

 the Carbonate of Lime. — Its action on Porcelain. — Additional appa- 

 ratus required in confequence of that action. — Good refults ; in par- 

 ticular, four experiments, illustrating the theory of Internal Calcina- 

 tion, and Jhe wing the efficacy of the Carbonic Acid as a Flux. 



Since I found that, with porcelain tubes, I could neither 

 confine the carbonic acid entirely, nor expofe the carbonate 

 in them to ftrong heats ; I at laft determined to lay them afide, 

 and return to barrels of iron, with which I had formerly ob- 

 tained fome good refults, favoured, perhaps, by fome acciden- 

 tal circumflances. 



On the 12th of February 1803, I began a feries of experi- 

 ments with gun-barrels, refuming my former method of working 

 with the fufible metal, and with lead; but altering the pofition of 

 the barrel from horizontal to vertical ; the breech being placed 

 upwards during the action of heat on the carbonate. This very 

 fimple improvement has been productive of advantages no lefs 

 remarkable, than in the cafe of the tubes of porcelain. In this 

 new pofition, the included air, quitting the air-tube on the fu- 

 fion of the metal, and rifing to the breech, is expofed to the 

 greateft heat of the furnace, and muft therefore react with its 

 greateft force ; whereas, in the horizontal pofition, that air 

 might go as far back as the fufion of the metal reached, where 

 its elafticity would be much feebler. The fame difpofition 

 enabled me to keep the muzzle of the barrel plunged, du- 

 ring the action of heat, in a vefiel filled with water ; which 



contributed 



