MODIFIED by COMPRESSION. 121 
the tube was encafed in-a folid mafs, before the heat had 
reached the mcluded moifture. The difficulty was to catch 
the fufible metal at the proper temperature ; for when it was 
fo hot as not to fix in a few feconds, by the contact of the 
cradle and its contents, the water was heard to bubble through 
the metal and efcape. I overcame this difficulty, however, 
by firft heating the breech of the barrel, (containing a fufh- 
cient quantity of fufible metal), almoft to rednefs, and then 
fetting it imto a veflel full of water, till the temperature had funk 
to the proper pitch, which I knew to be the cafe when the 
hifling noife produced in the water by the heated barrel cea- 
.fed; the cradle, during the laft ftage of this operation, being 
held clofe to the muzzle of the barrel, and ready to be thruft 
into it.’ 
On the 2d of May, I made my firft experiment im this way, 
ufing the fame air-tube as in the laft experiment, -which was 
equal in capacity to one-thirtieth of a cubic inch. Half a 
grain of water was introduced in the manner juft defcribed. 
The barrel, after an hour of red-heat, was let down by a 
‘rope and pulley, which I took care to ufe in all experiments, 
in which there was any appearance of danger. All was found. 
The metals rufhed out fmartly, and a flafh of. flame accompa- 
nied the difcharge. The upper pyrometer gave 24°, and the 
lower one 14°. The contents of the inner tube had loft lefs 
‘than 1 per cent., ftridtly 0.84. The carbonate was im a ftate of 
good limeftone ; but the heat had been too feeble: The lower 
part of the chalk in the little tube was not agglutinated: The 
chalk round the fragment of pipe-ftalk (ufed to introduce the 
water), which had been more heated than the pyrometer, and 
the {mall rod, which had moulded itfelf in the boll. of the 
ftalk, were in a ftate of marble. 
On the 4th of May, Imade an experiment like the laft, but with 
_ the addition of 1.05 grains water. After application of heat, the 
VoL. VI.—P. I. Q fire 
