MODIFIED by COMPRESSION. 12 
Us 
the inner tube, which it had filled completely, conftituting a 
real vein, like thofe of ‘the mineral kingdom: which is {till 
diftin@lly to be feen in the fpecimen. It had then {pread_ it- 
felf upon the outfide 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 firft conceive that the experiment was loft, 
and the barrel deftroyed: The barrel was vifibly fwelled, 
and in {welling had burft 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 fufions and the letter which I have 
been in the habit of cutting on thefe fmall pieces, in or- 
der to trace the degree of action upon them, was thus quite 
obliterated. On the lower end of the fame. lump, the letter 
is till vifible. Both the lump and the rammed chalk were 
ina good femitranfparent ftate, fhining a little in the fra@ture, 
but with no good facettes, and no where appear ing to have 
acted on the tube. This laft circumftance is of confequence, 
fince it feems to fhew, that this very remarkable action of 
heat, under compreflion, was performed without the affift- 
. ance of the fubflance of the tube, by which, in many other 
pl. experiments, 
