the Force ofjired Gunpowder. 24,1 
reposes upon its supporter, but something less above, being 
somewhat diminished, and rounded off at its upper extremity. 
Its bore, which, as I have already observed, is ^ of an inch in 
diameter, is 2.13 inches long, and it ends in a very narrow 
opening below, not more than 0.07 of an inch in diameter, and 
1.715 inch long, which forms the vent (if I may be permitted 
to apply that name to a passage which is not open at both ends), 
by which the fire is communicated to the charge. From the 
centre of the bottom of the barrel there is a projection of about 
0.45 of an inch in diameter, and 1.3 inch long, which forms 
the vent tube V. Fig. 3. is a view of an iron ball W, which 
being heated red-hot, and being applied to the vent tube by 
means of an hole O made in it for that purpose, fire is com- 
municated through the solid substance of the vent tube to the 
powder it contains, and from thence to the charge. 
Fig. 4. which is drawn on a scale of two inches to the inch, or 
half the real size of the machinery, shews how the barrel B was 
placed upon its support C ; how this last was placed upon its 
circular plate of iron D, and how the red-hot iron ball W was 
applied to the vent tube V. This ball is managed by means of 
a long handle h of iron, and being introduced through a cir- 
cular opening g in the support, and applied to the vent tube V, 
is kept in its place by means of a wedge, or rather lever /, 
whose external end is represented in the drawing as being 
broken off, to save room. The circular opening in front of the 
support is seen in front, and consequently more distinctly, in 
the drawing, fig. 1 . In this drawing the end of the vent tube 
may be likewise discovered through this opening; but as it was 
necessary, in order to introduce all the parts of this machinery, 
to make the drawing upon a very small scale, it was not possible 
