( w ) 
with my Theory of Friction, I was willing to try 
how the faid Theory would agree with Inch a Tackle 
of Pullies as is commonly ufed in Building. 
The firft Experiment was made with a Tackle of 
five Brafs Sheevers in Iron Frames or Blocks ; that is, 
three Sheevers in the upper Block, and two in the 
lower. 
Having made an Equilibrium, by hanging one 
Hundred and a quarter at the lower Block, and a 
quarter of an Hundred at the running Rope j I added 
1 7 Pounds and a half before the Power could go 
down and raile the Weight. 
Experiment x. Two Hundred and an half being 
balanced by half an Hundred, the Addition of 28 
Pounds made the Power raile the Weight. 
N. B. The Sheevers were five Inches Dia- 
meter, the Pins half an Inch, and the Rope three 
quarters. 
In the firft Experiment 17 Pounds and an half ex- 
ceeds by 4 Pounds and a half the Sum of the Fricti- 
ons deduced from the Theory. But in the fecond 
Experiment 18 Pounds exceeds the Sum of the Fricti- 
on but one Pound. 
The Reafon of this appeared to be, that the Rope 
at firft was too big for the Cheeks that held the Shee- 
vers; but in the fecond Experiment, where the Rope 
was more ftrerched, it was lomewhat diminilhed in 
Diameter, and fo brought off from rubbing fo hard 
agaiuft thole Cheeks. 
From knowing the Quantity of FriCtion a priori 
in fuch large Tackles, we may know what to expeCt 
in Practice : For if one Man, who for a finall time 
can exert the Force of one Hundred Pounds, thinks 
that 
