MODIFIED by COMPRESSION. 139 



flate of beautiful femitranfparency. (I have attempted to re- 

 prefent the entire fpecimen, as it flood 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 fubflance was unufually compact and 

 hard under the knife. The whole furface {ebac d, fig. 31.)? 

 and the infide of the air-bubbles, had a vitreous luflre. Thus, 

 every thing denoted a flate of vifc id fluidity, like that of ho- 

 ney. 



These lafl experiments feem to obviate every doubt that re- 

 mained with refpedl to the fufibility of the purefl carbonate, 

 without the affiftance of any foreign fubflance. 



VII. 



Meafurement of the Force required to conjlrain the Carbonic Acid. — Ap- 

 paratus with the Muzzle of the Barrel upwards y and the weight acting 

 by a long Lever. — Apparatus with the Muzzle downwards. — Appa- 

 ratus with Weight atling diredlly on the barrel. — Comparifon of various 

 refults. 



In order to determine, within certain limits at leafl, wliat 

 force had been exerted in the foregoing experiments, and what 

 was necefTary to enfure their fuccefs, I made a number of ex- 

 periments, in a mode nearly allied to that followed by Count 

 Rumford, in meafuring the explofive force of gunpowder. 



I began 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 



$ 2 inch, 



