300

THEORY AND PRACTICE

TRACT 37-

of an inch in the windage, viz, between the balls ofT96 and 1 86 diameter, that of the cylinder of the gun being2'02. And the quantity lost being as the spaces, and thespaces as the differences of the squares of the diameters ;therefore, as 1’96 2 - 1-86’- : J- : : 2‘02 2 — 1*96 2 : j-f ncarly =*21 nearly; and this is the part of the force lost by the wind-age between 2*02 and 1*96 diameters. There remains yet tobe computed the waste by the vent. If we estimate this inproportion to its magnitude, which will not be far from thetroth; and its diameter being nearly -J- °f an inch = "2;therefore as I*96 2 — 1’86 2 : f : : *2 2 : *04 nearly, the waste offorce bv the vent only. The two together make *25 or y,for the waste by the windage and vent with the usual ball ofI•96 diameter. On this account then we must increase eachof the numbers in the last tablet by the ~ part, by whichmeans they will then become as here annexed, for the severalvalues of the first force n.

Powder.

The Guns.

os

1

2

3

4

4

1700

1720

1784

1776

8

1821

2015

2241

2282

16

2075

2068

2264

2300

1 7 . 5 . Such then are finally the numbers denoting the va-lue of 77 , the first force of the inflamed elastic fluid, includingthe effect of heat, when occupying the space only filled bythe powder alone, before it was fired, when most of the ma-terial allowances are made; and which we thus find is aboutdouble of what Mr. Robins supposed it to be. With eachelrarge of powder, there is but very little difference amongall the four guns, being of equal diameter, though of verydifferent lengths; the numbers increasing but a very littlewith the longer guns, probably arising from the circumstanceof the powder acting rather a longer time on the ball in thelong guns, than in the shorter; a circumstance which verywell accounts for the small difference in the effect. But a