VOL. LXVIII.] PHILOSOPHICAL TRANSACTIONS. 293 



same as that of the former pendulum, their numbers of vibrations being alike in 

 the same time. Instead of suspending this pendulum, after the manner of the 

 former, by the ends of its axis in grooves turned to fit them, they were only 

 placed on flat, level pieces of wood, on which this pendulum vibrated much 

 freer than the other did ; but a small nail was driven into the supporting wood, 

 just behind each end of the axis, to prevent the stroke of the shot from throw- 

 ing it off" the stand. 



To this pendulum was adapted a better machine for the tape to slide through 

 than the former, the inconvenience of which had often been experienced by its 

 catching and entangling the tape, so as to interrupt its free motion, and once 

 indeed to break it. This new one, however, was at once very simple, and per- 

 fectly free from every inconvenience, giving just the necessary degree of friction 

 to the tape, without ever stopping its motion ; so that, of the real quantity 

 drawn out by the vibration of the pendulum, there could not possibly be the least 

 doubt. This simple contrivance consisted barely of about 6 or 8 inches of the 

 list of woollen cloth fastened on the arch of a small piece of wood, which was 

 shaped into the form of the segment of a circle thus /niiliif. , the tape being made 

 to pass through between the curved side and the list, which was moderately 

 stretched and fastened by its 1 ends to those of the little arch. 



On the whole, the machinery was all so perfect, and every circumstance at- 

 tending the experiments of the 2 ensuing days so carefully observed, that we 

 may with great safety rely on the conclusions resulting from them. And as 

 those of the one day were made with leaden balls, and those of the other with 

 iron ones, which differ greatly in weight, every other circumstance being the 

 same, they afford very good means for discovering the law of the different 

 weights of shot, while the variations in the powder from 2 to 4 and 8 ounces, 

 furnish us with the rule for the different quantities of it. 



The 4 th course was on the 20th of July, a fine clear day. The powder was 

 a mixture of several of the sorts made for government, and the balls were of 

 lead. The quantities of powder were 2, 4, and 8 ounces alternately ; and the 

 dimensions at first were thus : 



p = 552 pounds, the whole weight of the pendulum. 



r =: 101 inches, its whole length. 



g := 78 inches, the distance of the centre of gravity. 



A = 88 inches = 74- feet, that of the centre of oscillation. 



