8. Experiments zipon Gtmpowder, 



a, by Is the bar of the pendulum which is seen broken 

 off, as there is not room to shew the whole of its 

 length. 



c, dy are the pivots by which it was suspended, e is 

 the circular plate of the pendulum, to which f^ g^ two 

 circular targets, are fastened by screws, and by means 

 of the iron straps i, 2, 3, 4, which are nailed to the 

 edges of the targets. //, k^ are the hooks which served to 

 receive the pivots r, d^ of the pendulum. 



The hooks were firmly fixed to the horizontal beam 

 R, S, which supported the whole apparatus by means of 

 three screws, m^ n, 0, which passed through three holes In 

 the plate that connects the two hooks. When the hooks 

 are fastened to the beam, the middle screw, n^ was first 

 put into its place, and the pendulum was allowed to 

 settle itself in a position truly vertical, after which the 

 hooks were immoveably fixed by means of the screws 

 m^ 0. 



The chord of the arc through which the pendulum 

 ascended in each experiment was measured by a ribbon, 

 according to the method invented and described by Mr. 

 Robins. 



The recoil was measured in the following manner : 

 The barrel was suspended in an horizontal position (and 

 nearly in a line with the center of the target) by two 

 small pendulous rods 64 inches in length, and 25.6 

 inches asunder ; which, being parallel to each other, 

 and moving freely upon polished pivots, about the axes 

 of their suspension, and upon two pair of trunnions 

 that were fixed to the barrel, formed, together with the 

 barrel, a compound pendulum ; and from the lengths 

 of the vibrations of this pendulum, the velocity with 

 which the barrel began to recoil, or rather its greatest 

 velocity, was determined. 



