MODIFIED by COMPRESSION. 12 



.y 



the inner tube, which it had filled completely, conftituting a 

 real vein, like thofe of the mineral kingdom : which is ftill 

 diftin&ly to be feen in the fpecimen. It had then fpread it- 

 felf upon the outnde of the inner tube, to the extent of half 

 an inch in diameter, and had enveloped the fragment of por- 

 celain already mentioned. When pieces of the compound 

 were thrown into nitric acid, fome effervefced, and fome not. 

 I repeated this experiment on the fame day, with two 

 grains of water. The furnace being previoufly hot ; I conti- 

 nued the fire during one half-hour with the muffle open, and 

 another with a cover upon it. I then let the barrel down by 

 means of the pulley. The appearance of a large longitudinal 

 rent, made me at nrft conceive that the experiment was loft, 

 and the barrel deftroyed : The barrel was vilibly fwelled, 

 and in fwelling had bur ft the Cruft of fmooth oxide with 

 which it was furrounded ; at the fame time, no exudation 

 of metal had happened, and all was found. The metals 

 were thrown out with more fuddennefs and violence than 

 in any former experiment, but the rod remained in its place, 

 being fecured by a cord. The upper pyrometer gave 27 % 

 the lower 23 . The contents of the inner tube had loft 1.5 

 per cent. The upper end of the little lump of chalk, was 

 rounded and glazed by fufion> and the letter which I have 

 been in the habit of cutting on thefe fmall pieces, in or- 

 der to trace the degree of a&ion upon them, was thus quite 

 obliterated. On the lower end of the fame lump, the letter 

 is ftill vifible. Both the lump and the rammed chalk were 

 in a good femitranfparent ftate, mining a little in the fracture, 

 but with no good facettes, and no where appearing to have 

 acted on the tube. This laft circumftance is of confequence, 

 fince it feems to fliew, that this very remarkable action of 

 heat, under compreflion, was performed without the aftift- 

 ance of the fabftance of the tube, by which, in many other 



CL.2 experiments, 



