Graduation of AJlronomlcal Infruments • j? 
Propofed Improvements of Hindley’s Method* 
1 would recommend the number of parts into which the 
circle is to be reduced to be 1440; that is 4 times 360 ; which 
dlvifions will therefore be quarters of a degree ; the diftances 
of the holes in the chaps will therefore, to a three- feet radius, 
be T V~-o- of aii inch nearly ; that is, between the one-fixth and 
one-feventh of an inch diftance center and center* 
Having provided myfelf with a ftout mandrel, or arbor, for 
a chock Lathe , properly framed, that would turn a circle of fix 
feet diameter, I would prepare a chock, or platform, for the 
end of it, of that diameter, or a little more, compofed of 
clean-grained mahogany plank, all cut out of the fame log ; 
which, when finifhed, to be about if inch thick, and 
formed in fedlors of circles, fuppofe 16 to make the circle * 
the middle line of each fedtor lying in the direction of the 
grain of the wood, this will consequently every where point 
outward : the method of framing this kind of work is well 
known. 
The way of getting a flip of brafs to anfwer the circum- 
ference of this platform is fuggefted in Mr. Bird’s Account of 
conftrudting Mural Quadrants* Let a parallelogram of brafs 
of about three feet long, and of a competent fubftance (fup- 
pofe half an inch) to make it when finiflied about one-twen- 
tieth of an inch in thicknefs, be caft of the fineft brafs ; and 
this to be rolled down till it becomes of fufficient length for 
the hoop, and about one-fifth part more. I would then cut 
off, from the whole length, fomewhat better than one-fixth 
part, the whole being fufficiently reduced to a thicknefs by the 
rollers# Perhaps no way will be more ready and convenient to 
