148 On Cog or Toothed Wheels. 
. Thus I apprehend it is proved, that the ac- 
tion of a wheel of this kind, on another with 
which it geers, is perfectly uniform in res- 
pect of swiftness; and hence the proof that 
it is likewise so, as to the force communicated. 
Before I proceed to the second proposition, 
I ought perhaps to anticipate some objections 
that have been made to this system of geering, 
and which may have already occurred to some 
_gentlemenipresent. For example, it has been 
supposed that the friction of these teeth, is 
augmented by their inclination to the plane 
of the wheel ; but I dare presume to have al- 
ready proved, that it is this very obliquity, 
joined to the total absence of motion in di- 
rection of the axes,. that destroys the friction, 
instead of creating it. Tacknowledge however, 
that the pressure on the points of contact, is 
greater than it would be on teeth, parallel to 
the axes of the wheels, and I farther concede | 
that this pressure tends to displace the wheels _ 
in the direction of the axes, (unless this ten- 
dency is destroyed by a tooth, with two op- 
posite inclinations.) “Butsupposing this coun- 
teraction neglected, let us ascertain the im- 
portance of these objections. First, with 
regard to the increase of pressure on the point 
D on the line BC, (representing the oblique 
tooth in question,) relative to that which 
