158 On Cog or Toothed Wheels. 
them always anointed with oil and emery, one 
of the most destructive mixtures known for 
rubbing metals; but after this severe’ trial, 
the teeth of the wheels, at their primitive cir- 
cles were found as entire as before the experi- 
ment. And why? Certainly for no other 
reason than that they worked without sen- 
sible friction. 
Hitherto nothing has been said of wheels 
in the conical form, usually denominated mi- 
tre and bevel geer. But my models will prove, 
that'they are both comprehended in the system. 
The only condition of this unity of principle 
is, that the axes of two wheels, instead of 
being parallel to each other, be always found 
in the same plane. With this condition every 
property above-mentioned, extends to this 
class of wheels which my methods of execu- 
tion also include, as indeed they do jobs 2 
possible case of geering. 
Being afraid of trespassing on the time of the 
society, I have suppressed a part of this paper, 
perhaps'already too long; but I hopeI may be 
indulged with a few remarks on the application 
of those wheels to practical purposes. And 
first, asto what I have myselfseen ; these wheels 
have been used in several important machines 
to which they have given much swiftness, soft- 
ness or precision of motion as the case re- 
