6 Experiments iipon> Gunpowder. 



In order that every part of the apparatus employed 

 in these experiments might be as perfect as possible, 

 all the more delicate parts of it were executed by Mr. 

 Frazer, mathematical instrument maker in Duke's 

 Court, St. Martin's Lane, and, among the rest, all the 

 contrivances just described relative to the vent. 



The velocities of the bullets were determined by 

 means of a pendulum, according to the method invented 

 by Mr. Robins. 



The pendulum I made use of (Fig. 6) is composed of 

 a circular plate of hammered iron (a) 13 inches in 

 diameter and 0.65 of an inch thick, to which is firmly 

 fastened a bar of iron (<, <:,) 56.5 inches in length, 2.6 

 inches broad, and half an inch in thickness, by which it 

 is suspended, by means of two pivots (d, e\ at the end 

 of the bar (c) and at right angles to its length. These 

 pivots- being very accurately finished, and moving on 

 polished grooves, which were kept constantly oiled to 

 lessen the friction, the vibration of the pendulum was 

 very free, as appeared by the great length of time its 

 vibrations continued after it had been put in motion, 

 and was left to itself. To the circular plate of the pen- 

 dulum, targets of circular pieces of wood of different 

 thicknesses were fixed, which in the course of the experi- 

 ments were often spoiled and replaced ; and in order to 

 mark the weight and dimensions of the pendulum in 

 each experiment, the pendulums are numbered according 

 to the different targets that were made use of; and the 

 weight and dimensions of each pendulum are set down 

 in a table at the end of the description of the apparatus. 



The target of the pendulum No. i was made of a 

 circular piece of elm-plank, 3.} inches thick, and equal 

 in diameter to the iron plate of the pendulum to which 



