VOL. XXXVI.] I'HILOSOPHICAL TRANSACTIONS. 37g 



Thus far Mons. Perault. But however plausible this description may appear, 

 a little attention will show, that if this new engine had no friction, yet it is 

 more inconvenient than an axis in peritrochio with the same proportions; and 

 likewise that it has more friction than the same machine in the common use. 

 ACE, fig. 8, is a common axis in peritrochio, which has the wheel ae 5 times 

 larger in diameter than the axle; so that AC, the radius of the wheel, which 

 is the distance of the power, is to CB the radius of the axle, the distance of the 

 weight, as 5 to I : consequently 1 oz. for example, will keep 5 in equilibrio. 

 Now though the friction of the gudgeon at c is unavoidable, yet it may be di- 

 minished by diminishing the diameter of the gudgeon, provided it remains 

 strong enough to sustain the machine and its burthen. Here one penny- 

 weight, or -jV of the power added to it, makes it preponderate, and give the 

 machine motion with a due velocity. 



Now this very engine, used in Mons. Perault's way, so alters the dis- 

 tances of the weight and power, that instead of one for our power, we must 

 have 2-1- to keep the very same weight 5, in equilibrio, as may appear by a 

 sight of the fig. Q, where, since in the action of the machine, when we pull the 

 rope PA, we make the axle db to wind itself up on the rope hd, it is evident 

 that D is now become the centre of motion, db (the whole thickness of the 

 axis) the distance of the weight = 2; and the distance of the power is re- 

 duced to AD = 4. So that if 2 men, having been employed in the common 

 way to raise weights equal to the strength of 10 men, an engineer should alter 

 the manner of working, and fit up the axis in peritrochio in Mons. Perault's 

 way, instead of gaining an advantage, he must call in 3 more men to perform 

 the work. If it be answered, that what is lost in strength, will be gained in 

 time, it may not only be said, that one cannot always call in more help on the 

 sudden, but that even then, though we should not call this an inconveniency, 

 yet there will be still more friction in this than in the common method; for 

 the roller or axle will find a difficulty to wind on the rope, because they are 

 not perfectly pliable, and the less so, the greater the weight is that stretches 

 them. This, together with the friction of the collar of the rope of the coun- 

 terpoise to the engine, makes the hindrance greater than in the common way. 

 For it appears by experiment, that when the power is become equal to 2J-, to 

 keep the weight 5 in equilibrio, there must be added -f (here 4-penny-weight) 

 to put the power in motion. 



And to show that this friction of the ropes is not always the same as Mons. 

 Perault supposes it; when p, or the power, is made only 1 oz. and w, or the 

 weight, 2 oz. then to make the power preponderate, only 1 penny-weight and 

 3 c 2 



