MODIFIED ly COMPRESSION. 89 
Il. 
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 with a view 
to thefe Experiments.—The Vertical Apparatus adopted.—View of 
Refults obtained, both in Iron and Porcelain.—The Formation of Lime- 
ftone and Marble.—Inquiry into the Caufe of the partial Calcinations. 
—Tubes of Porcelain weighed previous to breaking.—Experiments with 
Porcelain Tubes proved to be limited. 
Waite I was carrying on the above-mentioned experiments, 
I was occafionally occupied with another fet, in tubes of por- 
celain. So much, indeed, was I prepoffeffed in favour of this 
laft mode, that I laid gun-barrels afide, and adhered to it du- 
ring more than a year. The methods followed with this fub- 
ftance, differ widely from thofe already defcribed, though 
founded on the fame general principles. 
I procureD from Mr WEpcwoop’s manufactory at Etruria, 
in Staffordthire, a fet of tubes for this purpofe, formed of the 
fame fubftance with the white mortars, in common ufe, made 
there... Thefe tubes were fourteen inches long, with a bore 
of half an inch diameter, and thicknefs of 0.23 being clofed 
at one end (figs. 9, 10, II, 12, 13.) 
I proposeD to ram the reer of lime into the breech 
(Fig. 9. A); then filling the tube to within a finall diftance of 
its muzzle with pounded flint (B), to fill that remainder (C) 
with common borax’of the fhops (borat of foda) previoufly res 
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 
requifite heat to the cgrbonate lodged in the breech. 
Vou. VI.—P. I. M Res 
