94 EFFECTS of HEAT 
ged into the fand, (as in fig. 17.), and the breech introduced 
into the muffle. In feveral experiments, I found it anfwer 
well, to occupy great part of the fpace next the muzzle, with 
a rod of fand and clay previoufly baked, (fig. 19. KK), which 
was either introduced at firft, along with the pounded borax, 
or, being made red hot, was plunged into it when in a liquid 
ftate. In many cafes I aflifted the compactnefs of the tube by 
means of an internal glaze of borax; the carbonate being pla- 
ced in a {mall tube, (as fhewn in fig. 18.) 
Turse devices anfwered the end propofed: Three-fourths 
of the tube next the muzzle was found completely filled with 
a mafs, having a concave termination at both ends, (f and g 
figs. 17. 18. 19.), fhewing that it had ftood as a liquid in the 
two oppofite pofitions in which heat had been applied to it. 
So great a degree of tightnefs indeed was obtained in this 
way, that I found myfelf fubjected to an unforefeen fource of 
failure. A number of the tubes failed, not by explofion, but 
. by the formation of a minute longitudinal fiffure at the breech, 
through which the borax and carbonic acid efcaped. I faw 
that this arofe from the expanfion of the borax when in a li- 
quid ftate, as happened with the fufible metal in the experi- 
ments with iron-barrels ; for, the crevice here formed, indi- 
cated the exertion of fome force acting very powerfully, and 
to a very fimall diftance. Accordingly, this fource of failure 
was remedied by the introduction of a very fmall air-tube. 
This, however, was ufed only in a few experiments. 
In the courfe of the years 1801, 1802, and 1803, I made a 
number of experiments, by the various methods above defcrib- 
ed, amounting, together with thofe made in gun-barrels, to 
one hundred and fifty-fix. In an operation fo new, and in 
which the apparatus was ftrained to the utmoft of its power, 
conftant fuccefs could not be expected, and in fact many expe- 
riments failed, wholly or partially. The refults, however, upon 
the 
