[ r 59 ] 
preffure will be equal on each wheel ; and the greater 
the preffure, the more fecurely they are kept in their 
proper places. I have a double fet of brafs wheels, 
8 inches diameter, with which I have made feveral 
experiments, and find the pradice anfwer as near as 
poffible to the theory. But as the expence of brafs 
wheels, to large engines, would be very confiderable, 
had wheels made of wood, which I find to anfwer 
tne purpofe as well, if not better ; as they are much 
lighter , and may be made ffrong enough to fupport 
a great weight, at a moderate expence. 
The wooden wheels are fixed on an arbour, whofe 
pevets have been turned true, and the edge of the 
wheel turned after it is fixed on the arbour. Thefe 
v/heels are placed in a wooden frame, with a fmall 
plate of brafs fixed properly in the frame, for the 
pevets to turn in. They may be made with fpokes, 
and fellies, capable of fuftaining a confiderable weight; 
and there is no danger of their wearing, as the pevet 
only rolls on the edge. I had wheels made of white 
deal, with feveral lamina glewed together, eroding 
each other in different diredions of the grain of the 
wood, which hinders them from warping, or crack- 
ing ; and which I found, upon trial, anfwered ex- 
tremely well. By eroding the grain of the wood, 
the oppofition to the preffure on the periphery is pret- 
ty equal in all parts; and the edge of the wheel, in a 
little time, becomes as fmooth, and almoff as hard as 
brafs. 
Thefe wheels cannot be applied to wheel carriages, 
unlefs they were to move on very even ground, as 
fudden jerks, and turnings, would foon diforder 
them. But they may certainly be employed to ad- 
1 vantage 
&> 
