ACTION OF HEAT, &C# ,3SJ 



III. 



Account of a Series of Experiments, Jhezving the Effects of Com- 

 prejjion in viodifying the ASiion of Heat, £j/ Sik. Jamss 

 Hall, Bart. F. R. S. Edinburgh. 



(Concluded from Page 328.) 



Section III. 

 Experiments made in Tubes of Porcelain. — Tubes of Wedgwood's 

 Ware. — Methods ufed to confine the carbonic Acid, and to 

 clofe the Pores of the Porcelain in a horizontal Apparatus. — 

 Tubes made vjith a View to thefe Experiments, — The vertical 

 Apparatus adopted. — View of Refults obtained^ both in Iron 

 and Porcelain. — The Formation of Lime-jlone and Marble. — 

 Inquiry into the Caufe of the partkd Calcinations. — Tubes of 

 Porcelain weighed previous to breaking—^ Experiments xdtk 

 Porcelain Tubes proved to be limited. 



Wj 



HILE I was carrying on the above-mentioned experi- Set of experi- 

 ments, I was occafionally occupied with another fef, in tubes "^^"''^.^.'^^5^^^* 

 of porcelain. So much, indeed, was I prepoITeflTed in favour 

 of this laft mode, that I laid gun-barrels afide, and adhered tq 

 it during more than a year. The methods followed with this 

 fubftance differ widely from thofe already defcribed, though 

 founded on the fame general principles, 



I procured from Mr. Wedgwood's manufadory at Elruria, 

 in Stafford (hire, a let of tubes for this purpofe, formed of the 

 fame fubftance with the white morlars, in common ufe, made 

 there. Thefe tubes were fourteen inches long, with a bore 

 of half an inch diameter, and thicknefs of 0.2; being clofed 

 at one end (figs. 9, 10, 11, 12, 13.) F/. XI. 



I propofed to ram the carbonate of lime into the breech They were clofed 

 {Fig, 9. A) ; then filling the lube to within a fmall difiance of ^j^^ ^^^^^ ^ _ 

 its muzzle with pounded flint (B), to fill that remainder (C) tuie was ftopped 

 with com-mon borax of the fhops (borat of foda) previoufly fe- "^^^^^^ ^ 

 duced to glafs, and then pounded; to apply heat to the muzzle 

 alone, fo as to convert that borax into folid glafs ; then, re- 

 verfing the operation, to keep the muzzle cold, and apply the 

 lequifite heat to the carbonate lodged in the breech. 



I thus expected to confine the carbonic acid; but the at- Difficulties of 

 tempt was attended with confiderable difficulty, and has led "^^'^ proccfs. 

 2 to 



