[ i57 3 
mounting to 162 chaldrons in a year’s conftant work; 
which is a very confiderable article, even where coals 
are to be had at a cheap price. 
It may be proper to obferve that the archeads C 
of the leaver, muft be drawn from the center of the 
fmall part b of the pevet, which turns on the qua- 
drants. The quadrants and frame muft be made 
fufficiently ftrong, which I had made of caft iron. 
The pevets of the quadrants are made of tempered 
fteel, and turned true. There are four pillars G in 
the back plate of the frame, with fhoulders, and 
ftrong fcrews, which pafs through the fore plate, and 
are fcrewed tight by a nut z, when the quadrants are 
placed in the frame. 
The back plate E (fig. 4.) of the frame, is longer 
than the fore plate F, in order to admit the iron bolts 
G at each end ; by which the frame is fcrewed to a 
wooden block. The edges of the frame reft on a 
broad plate of iron, laid on a level board; upon 
which the blocks and frames are placed, and bolted 
down in the ufual manner. The holes that the pe- 
vets of the quadrants turn in, are made in fquare 
pieces of brafs e, riveted for the purpofe into the frame 
plates. 
The round part b , of the axis B, fig. 4, is made 
of hardened fteel, and the edges g of the quadrants 
are alfo of the fame metal ; otherwife the very great 
weight they fuftain, would make a deep impreftion 
in that part. There are two fprings, h h> to each qua- 
drant, which keep them in their proper places, and 
yield eafily to the motion of the quadrants. 
There was great care taken to make the frame 
fquare, and place the quadrants upright and level ; 
and 
