Ijga 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1778. 



the height of the charge, shows the degree of compactness with which the 

 powder was lodged in the piece. The dimensions, as taken this day, were thus: 



p = 324 pounds, the weight of this pendulum. 



g =1 7 1 .4 inches, the distance of the centre of gravity. 



h = 88 inches = 7t feet, the distance of the centre of oscillation. 



r =■ 1 02i inches, the whole length to the tape. 



Here the common mean weight of the ball is 18f ounces, the mean velo- 

 city with 2 oz. of powder is 738, and that with 4 oz. of powder is 1043 feet 

 per second. The ratio of these 1 velocities, is that of 1 to 1.414: that is, 

 accurately the ratio of the square roots of the quantities of powder. 



Of the Experiments made with the id Petidu/um. — The 1st pendulum was 

 gradually more and more rent and shattered by the firing of so many balls into 

 it, till at the end of the last course of experiments it had become quite useless. 

 Another was then fitted up, and with it were performed the 2 following courses. 

 This 2d pendulum consisted of a cubical block of sound elm, of nearly 2 feet 

 long, fixed to the iron stem, but not exactly in the manner of the former; for 

 in this the stem was placed vertically over the centre of the top end, to which 

 point it continued whole, but there divided in 2, each passing to the right and 

 left over the top, down the sides, and returning along the bottom, and being 

 at proper intervals fastened to the wood with iron pins. A thick sheet of lead 

 was fastened over each of the 2 upright faces into wliicli the shot were to be fired, 

 both to guard them from splintering very much, and to add to the weight of the 

 pendulum. The whole was then firmly secured by 2 very thick iron bands or 

 hoops, passed horizontally quite around the wood, and firmly fixed to it, the one 

 next the upper end, and the other near the lower, so as strongly to resist the 

 endeavours of the shot to split the wood. 



The whole weight of the pendulum, thus fitted up, was 552 pounds; its 

 whole length, from tlic middle of the axis to the tape at the bottom, was 101 

 inches; the distance to the centre of gravity was 78 inches; and the distance to 

 the centre of oscillation was 88 inches, equal to 74- feet, which was exactly the 



