k

FIRED GUN-POWDER. 63

it at a proper height; suspend from 0 0 by the hooks 12, 12,and the chain n, a bason loaded with different weights tillthe bar breaks. The weight necessary to overcome the co-hefion of the bar S S being thus known, in the theorem“ 9962»S = P put its value expressed in pounds, and substitute

in the place of S the value of the pin O P, then the value of» will be found.

136. This machine may be combined in another manner.Instead of the canal O P, and the other parts placed belowC D ; 2, 3, is a cylindrical cavity, which is exactly filled withan iron pin 2, 3. in contact with an iron plate, 5, 5, letinto the thickness of metal of the cylinder, the exterior fideof which, 4, 4, is even with the superficies of the cylin-der. 6, 7, is an iron ring which goes round the cylinderABCD, fitting it exactly opposite to 2, 3, and so pro-portioned that the interior surface touch the plate of iron

f 4, 4. After each discharge, the ring is filed in the partj, 7, till it gives way to the action of the powder; takingcare to place the machine contiguous to a solid body, thatit may confine the plate 4, 5, and 2, 3, after breaking thering, for reasons already pointed out. The proper thick-ness for the ring having been determined, find the weight thatI can break another ring of the same metal and equal to it in

thickness; for this purpose, apply the ring to a short cylinderof hard wood of proper dimensions; let the plate 4, 4, belonger than the wooden cylinder that the iron hook 0,11,0may be hung on the ends. Make use of the same plate,4, 4, and the same ring, that the part which presses thering may not be altered in form from the action ofthe weight that is to break it. When the weight = P isthus found, to know the elasticity — n ; a particular the-f orem must be constructed, in which must be inserted the

values of the pin 2, 3, of the radius of the interior circum-ference of the ring, and of the thickness of metal at the partwhere the ring broke.

137. It results from these experiments f 133,134,135) thatif a vellel be filled with small-grained powder without beingcompressed, the greatest elasticity = « will be equal in dryweather to iqco hundred times the mean pressure of the at-mosphere, and only 1400 when the air is much loaded withvapour ; powder is therefore a kind of aerometer.

In this machine the diameter and height of the hollow cy-linder were each i an inch, and the contents about 3 drs.

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