[ 193 ] 



XXXIV. Account of a Series of Erpsrimenls, showing the 

 Effecls of Compression in modifijiiig the Action of Heat. 

 Bii Sir James Rall, Bart. F.R.S. Edin. 



[Continued from p. 155.] 



III. Experiments made in Tales of Porcelain. — Tuhes of 

 JJedgewood's JVare. — Methods used to confine the Car- 

 Ionic Acid, and to close the Pores of the Porcelain in a 

 horizontal Apparatus. -^Tuhes made lutth a View to these 

 Experiments. — The Vertical Apparatus adopted. — View 

 of Results obtained both in Iron and Porcelain. — The 

 Formation of Limestone and Alarble.^-Inqniry into the 

 Cause of the partial Calcinations. — Tubes of Porcelain 

 weighed previous to breaking. — Experiments with PorcC' 

 lain Tubes proved to he limited. 



W HiLE T was carrying on the aliove-inenlioncd experi- 

 ments, I was occasionally occupied with another set, in 

 tubes of porcelain. So much, indeed, was T prepossessed 

 in favour of this last mode, that I laid gun-barrels aside, 

 and adhered to it during more than a year. The methods 

 followed with this substance differ widely from those already 

 described, though founded on the sime general principles, 



I procured from Mr. Wcdgewood's manufactory at Etru- 

 ria, in Staffordshire, a set of tubes for this purpose, formed 

 of the same substance with the white mortars, in common 

 use, made there. These tubes were fourteen inches long, 

 with a bore of half an inch diameter, and thickness of 0*2 } 

 being closed at one end (figs. 9, 10, I J, 12, 13*). 



I proposed to ram the carbonate of lime into the breech 

 (fig. 9. A); then filling the tube to within a small distance 

 of its muzzle with pounded flint (B), to fill that remainder 

 (C) with common borax of the shops (borate of soda) pre- 

 viously reduced to glass, and then pounded ; to apply heat 

 to the muzzle alone, so as to convert that borax into solid 

 glass ; then, reversing the operation, to keep the muzzle 



* Plate IV , given in our last Number, 

 Vol. 24. No. 95. April 1806. N cold, 



