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NEW EXPERIMENTS

TRACT 34.

that point of the pendulum. The height descended beingthus known, the velocity acquired in falling through thatheight becomes known also, from the common rules for thedescent of bodies by the force of gravity. And the velocityof this centre, thus obtained, is to be esteemed the velocityof the whole pendulum itself; which being now given, thatof the ball before the stroke becomes known, from the givenweights of the ball and pendulum. Thus then, the deter-mination of the veiy great velocity of the ball, is reducedto the sifnplc mensuration of the magnitude of the arch de-scribed by the. pendulum, inconsequence of the blow struck.

8. Now this arch may be determined in various ways: irsthe following experiments it was ascertained by measuringthe length of its chord, which is the most useful line aboutit for. making the calculations by ; and this chord was mea-sured sometimes by means of a piece of tape or narrow rib-bon, the one end of which was fastened to the bottom ofthe pendulum, and the rest of it made to slide throughar small machine contrived for the purpose; and sometimesit was measured by the trace of the fine point of a stylettein the bottom of the pendulum, made in an arch just belowit, concentric with the axis, and covered with a composi-tion of a proper consistence; which will be particularlydescribed hereafter.

9 . Another similar method of measuring the great velocityof the ball is, by observing the arch of recoil of the gun,when it is hung also after the manner of a pendulum : for,by loading the gun with adventitious weight, it ma}'’ bemade so heavy, as to swing any convenient extent of archwe please; which arch it is evident will be greater or lessaccording to the velocity of the ball, or force of the inflamedpowder, since action and reaction are equal and contrary;that is, the velocity of the ball will be greater than thevelocity of the centre of oscillation of the gun, in the sameproportion as the v r eight of the gun exceeds the weightof the ball. And therefore, if the velocity of the centre ofoscillation of the gun be computed, from the chord of the