THE WINDAGE.

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that if the gun have any of the defects mentioned in the pre-ceding chapter, the fliot will strike against it, whatever bethe windage; but w ith this difference, that if the shot beginto move in an oblique direction, the less the windage andthe longer the bore, the more frequent will be the shocks;this is too evident to need illustration.

63. Our theory of the inflammation and explosion ofpowder destroys every idea of rays of fire (61), and provesthat the greatest force obtained from equal quantities of pow-der burned in vessels of different figures is in that whtre allthe powder is collected the nearest to the vent, by whichmeans a greater number of grains are fired; or where the fire ofthe first-generated fluid is reflected which increases the inten-sity of the heat, and produces more fluid in a given time; or,cœterh paribus from a proper combination of these two cir-cumstances : hence, curvilinear chambers in mortars, par-ticularly spherical ones, causing a quicker ignition, [ought togive longer ranges than cylindric chambers. To prove by asimple experiment that the property which burning mirrorshave from their figure of concentrating the solar rays, has noeffect in increasing the force of powder fired in a vessel of asimilar figure; two 16 prs. were constructed on purposeat Turin in 1730. (PI. 1, Fig. 3) A parabolic chamberCAD was made at the bottom C D of the bore F C D Gof one of these guns, the axis of the parabola was in thetriplicate ratio of the calibre of the gun, the vent corre-sponding to its focus : the other gun was of the same weightand length, its bore cylindric as F K L G, with the ventplaced at the bottom. These two guns were charged withequal quantities of powder, which exactly filled the parabolicchamber and were laid at 3 0 of elevation; the gun with thecylindric chamber ranged 414 yards farther than that withthe parabolic chamber.

CHAP.