MODIFIED ty COMPRESSION. Pe 
tapering from 1 inch to 0.6... Their thicknefs was about 0.3 
at the breech, and tapered towards the muzzle to the thinnefs 
of a wafer. 
_ I now adopted a new mode of operation, placing the tube 
vertically, and: not horizontally, as before. By obferving the 
thin-ftate of borax whilft in fufion, I was convinced, that it 
ought to be treated as a complete liquid, which being fupport- 
ed in the courfe of the experiment from below, would fecure 
perfect tightnefs, and obviate the failure which often happen- 
ed in the horizontal ppition; from the falling of the borax to 
the lower fide. 
In this view, (fig: 16.); I filled the breech in the manner 
defcribed above, and introduced into the muzzle fome: bo- 
rax (C) fupported at the middle of the tube by a quantity: 
of filex mixed with bottle-glafs (B). I placed the tube, fo 
prepared, with its breech plunged into a crucible filled with 
fand (E), and. its muzzle: pointing upwards. It was now my 
object to: apply’ sheat to the muzzle-half, whilft the other re- 
mained cold. In that view, I conftruéted a furnace (fig. 14. 
and. 1'5.),° ‘having a muffle placed vertically (cd), furround- 
ed on all fides with fire-(¢¢), and open both above (at c), 
and ‘below’ (at 'd). » The crucible juft mentioned, with its. 
tube, being then placed on a fupport directly below the ver-. 
tical muffle, (as reprefented in fig. 14. at F), it was raifed, fo 
that the half of the tube next the muzzle was introduced into. 
the fire. In’ confequence of this, the borax was feen from 
above to melt, and run down in the tube, the air contained in. 
the powder efcaping in the form of bubbles, till at laft the. 
borax ftood with a clear and fteady furface like that of wa- 
ter. ‘Some of this falt being thrown in from above, by means of 
a tube of glafs, the liquid furface was raifed nearly tothe muz- 
_ ale, and, after all had been allowed to become cold, the po-. 
fition of the tube was reverfed; the muzzle being now plun- 
ged. 
