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Corol. i. Hence it follows, that augmenting the 
length of the fail, without augmenting the quantity 
of cloth, does is not increafe the power ; becaufe 
what is gained by the length of the lever, is loft by 
the flownefs of the rotation. 
Corol. 2. If fails are increafed in length, the 
breadth remaining the fame, the effedft will be as the 
radius. 
VI. Concerning the velocity of the extremities of 
windmill fails , in refpeti to the Velocity of the 
wind . 
Maxim p. The velocity of the extremities of Dutch 
fails, as well as of the enlarged fails, in all their ufual 
pofitions when unloaded , or even loaded to a maximum , 
are confderably quicker than the velocity of the 
wind. 
The Dutch fails unloaded, as in Tab. 3. N° 8. 
made 120 revolutions in ya": the diameter of the 
fails being 3 feet 6 inches, the velocity of their ex- 
tremities will be 25,4 feet in a fecond; but the velo- 
city of the wind producing it, being 6 feet in the 
fame time, we jfhall have 6 : 25,4 : : 1 : 4,2 j in this 
cafe therefore, the velocity of their extremities was 
4,2 times greater than that of the wind. In like 
manner, the relative velocity of the wind, to the ex- 
tremities of the fame fails, when loaded to a maxi- 
mum , making then 93 turns in 52", will be found to 
be as 1 : 3,3 j or 3,3 times quicker than that of the 
wind. 
Vol. LI. 
Y 
The 
