MODIFIED ly COMPRESSION. 139 
ftate of beautiful femitranfparency. (I have attempted to re- 
prefent the entire fpecimen, as it ftood.on its cone of wax, in 
fig. 34.). The carbonate, where moulded on the platina, had 
a clean pearly whitenefs, with a faline appearance externally, 
and in the fun, fhone with facettes. Its furface was interrupt- 
ted by a few fcattered air-bubbles, which had lain againft the 
tube. The intervening fubftance was unufually compact and 
hard under the knife. The whole furface (eb aed, fig. 31.), 
and the infide of the air-bubbles, had a vitreous luftre. Thus; 
every thing denoted a ftate of ‘vifcid. giver like that: of hos 
ne 
pant laft experiments feet: to obviate every ars that re- 
mained with refpect to the fufibility of the pureft carbonate, 
without the affiftance of any foreign fubftance. 
VIL. 
Meafurement of the Force required to conftrain the Carbonic Acid.—Ap- 
© paratus with the Muzzle of the Barrel upwards, and the weight acting 
«by a long Lever.—Apparatus with the. Muxzle downwards. Appa- 
ratus with Weight acting direétly on the barrel.—Comparifon of various 
refults. 
In order to determine, within certain limits at leaft, What 
force had been exerted in the foregoing experiments, and what 
was neceffary to enfure their fuccefs, I made a number of ex- 
periments, in a mode nearly allied to that followed by Count 
Rumrorp, in meafuring the explofive force of gunpowder. 
I secan to ufe the following fimple apparatus in ‘June 
1803. I took one of the barrels, made as above defcribed, 
for the purpofe of compreffion, having a bore of 0.75 of an 
72 inch, 
