Graduation of Agronomical Tnjlruments . 
Reel, with a hole in it, to receive the other end of the drill to 
keep it at right-angles to the plane of the plate. This piece 
was a fpring, which bended at the end, where it was faftened 
to the frame of the lathe, at about eighteen inches from the end 
of the drill ; fo it puftied the drill through with any given force 
the drill would bear : and though that end of the drill moved 
in the arch of a circle, it was a very fmall part of it, being na 
more than equal to the thicknefs of the dividing plate. 
My good wifhes conclude me yours, 
Hen. Hxndley. 
Whoever attentively confiders the communication contained 
in the above letters will fee, that more happy expedients could 
not have been devifed to procure a fet of divifions, where there 
fhould be the moft exa£t equality among neighbours ; and 
which, for the purpofes of clock-making, is the principal thing 
to be wifhed for. But herein, as in M. Roemer’s method, there 
were no means of checking the diftant divifions, which run on 
to 360 : now fuch a check, when the expanficn of metals is con- 
fidered, and particularly the difference of expanfion between 
brafs and Reel, feems abfolutely neceffary for the purpofe of 
divifions upon inftruments, where the accurate menfuration of 
large angles is required, as much as the equality of neigh- 
bouring divifions^. 
With this view the invention of this ingenious perfon fug- 
gefted to him the thought of making his curved fcrew to lay 
* The ingenious Mr. Stancliffe (fome years a workman of Hindley’s) has 
fuggeited, that the difference of expanfion between the Heel chaps and the brafs 
hoop may be avoided by making the chaps of brafs alfo, with hard Heel holes fet 
feparately therein, fomewhat fimilar to the jewelled holes of watches. 
E 3 
hold 
