324 On Printing Presses and their Theory. 
gb: Aa. *4::OB+A0. cos? A: AO. cos? A. Divi- 
ding the and and fourth terms by = 
ee: we obtain, gb: 
Aa: : OB+A0. cos? a: AO. ak eae gb pe siacee 
AO -cos*? A+OB.—If the angle BCA be not too large, 
we may suppose C immoveable, and the whole resistance ap- 
plied atA. We shall then have power : resistance applied 
at A::2AO-sin A: : AO-cos? A+-OB. 
Cor. When A is so small that cos? A may be consider- 
as = I, power : resistance :: 2AO sin. A: AB. When 
the two ends B,B’, are immediately applied to each sets 
as in Prop. I. the ratio is that of 2'sin A: 1. Hence when 
two levers act by circular cheeks, they furnish a coke 
a rho — than that of two simple levers of i 
e same angle of obliquity, in the ratio e 
raf the lever to the excess of this length above the ra- 
dine of curvature of the cheek. wie side ee 
_ Prop. VIL. Let two equal rods AB, A’B' (Fig. 7) resting 
on the Spriestte sw pas A,A’, ‘Support the ae ay aad 
et this ] site be capa ble of turning round and slidi 
‘ it onthe fixed | line CF, which passes io its centre 
the middle of AA’: - 
if DE be cease parallel to CA, the power acting at the cir- 
cumference B, is to the weight resting on B'EB which it 
will support, as the sine of BDE to radius CA, is — ee 
£ivUiil 
ae * This 3 principle (which: may be called that of ma elie oilers) has 
it I serve Hebe inquiry whether the immense power which er wg thus com- 
does not admit of being advantageously introduced into certain kinds 
inery, Possibly it would be an improv t to construct the adja- 
ends of the two main levers of NVelis’ pr is form. 
Id be cary to assign the ratio of the power to the resistance for differ- 
CB’, w D, B ptie arches havi 
for their semitransverse axes, But result would be of no prac- 
of the difficulty of grinding the surfaces BD B’D 
ese 
‘De ta. vequal tot 
the Cor. preset ali Bo obliquities, if BO, 
