FIRED GUN-POWDER.’ (5$

per, the paper will sometimes be but little damaged. Thisdifference of effects proves how much the activity of the firevaries; hence, also the elasticity of the fluid must have al-tered very considerably during the course of these experiments.This will explain the reason why fire-arms soon becomeheated, and the vents enlarged after firing several roundswith wads strongly rammed; while the fame effects do nottake place when the wads are lightly rammed, though thefame quantity of powder be used with the same intervals oftime between the discharges.

By the experiments with the screw EFMN, the metal best-adapted for making touches for guns might be ascertained.Make a truncated cone of each of the metals intended to beproved, and place it in MNRS; that which sustains theaction qf the powdpr, with the least alteration, is the best.

CHAP. III.

Of the Modifications in the Generation of

THE ELASTIC FLUID IN THE CYLINDRIC BoRE OF

Fire-arms, when an Obstacle is presented to

it’s PASSING THROUGH THE MoUTH OF THE PlECE.

V

140. HEN the charge is not too small, nor the gun

too long, the shot in pasting from the charging cylinder to themouth of the piece is impelled by fresh elastic fluid, which iscontinually generating. This accelerated motion is the ef-fect of the pressure of the fluid, whenever the shot has beenstrongly rammed upon the powder; when it encounters otherobstacles as in rifled barrels ; or, when at the commence-ment of its motion, the resistance is equal or superior tothe impulsion of the fluid, which endeavours to expand itselftowardst he mouth of the piece. But if there be no resistance ;or only such as the impulsion can easily overcome, as whenthe charge is not wadded, or but slightly ; or when the wadover the powder is made of substances easily penetrable by theelastic fluid, as twisted hay or straw, the movement will thenbe the effect of impulsion. In the first cafe the velocity ateach point of the length of the bore is in the fubduplicateratio of the superficies, that expresses the sum of the pressure*in the spaces passed through by the shot; but in the second

5 K