[ ?S>8 ] 
by the Eye. The Surgeon being placed, the Af- 
Bftant who is to conduCt the Extremity of the Lever, 
works it according to his Directions, but perfectly 
flowly, that the Extenfions may be made with lefs 
Pain, and more effectually. 
If the Luxation is below, it is fufficient for its 
Reduction to lower the Extremity of the Lever, as is 
done with the Arnbe of Hippocrates. But here ap- 
pears a great Difference between the working or 
playing of thefe Two Sorts of Levers. The Ambe of 
Hippocrates is a plain Lever B , Fig. 2. TAB. IV. the 
Motion of which is from A to a, and confequently 
has for its Extenfton only the Space C, a, when it is 
brought to its laft Term of becoming perpendicular, 
a, b , whilft it has all A, C, or 1, rf, for its Elevation. 
The Ambe of Hippocrates therefore almoft only raifes 
the Bone of the Arm, without fcarcely ftretching it; 
and this is the DefeCt, which M. 4 Petit with Reafon 
blames it for ; and which is hill more fenlible, if one 
takes the ACtion of the Lever in the Point where- 
abouts it muft meet the Edge of the Cavity, and 
may caufe thofe Mifchiefs that are apprehended from 
it; but inftead of placing the fixed Point of that 
Lever in r, lower it to 2, by the means of the Tenant 
1,2; then the Direction of the End of the Lever 
becomes A-> E j its Elevation is but i,hy and theEx- 
tention it produces is A, E, or Z>, E: If you lower 
Bill the Lever’s Point of Reft, as in 3, by a longer 
Spur, the Elevation of its Extremity is reduced to 
ijky and the Extenfion it produces, reaches from A 
to F, if one carries thofe Levers as far as they will 
go, which is never necefiary. In fhort, it will be in 
your Power to give to this Lever an Extenfton as great 
as 
