[ '70 ] 
whereon the Index turned, was changed whenever it 
moved ever fo little; and, confequently, that the 
Arch (truck by the End B muft be irregular. 
On confidering this, I toothed two Pieces of Brafs, 
as 1,2, and 3, 4 (See Fig . $.) to fit each other fo ex- 
aftly, that, upon the leaft Motion of the one, the 
other would move ; then, fixing the Index upon the 
Centre C, its Motions were rendered much more re- 
gular. 
I placed likewife a little Collar of Brafs at B, upon 
the Cord S R y and to that Collar tied the Silk, which 
gave Motion to the Index, that the Cord S R might 
twift and untwift without any Impediment., 
If there is no Weight placed at Bottom, as in Fig . 
4 X the Piece of Brafs 1, 2 muft be fo heavy as to 
keep the Cord SB R at a convenient Tightnefs, and 
alfo to counterbalance the End of the Index CE y pro 
vided it be heavier than the other. 
The Length of the Cord SB R y itsThicknefs, and 
the Manner of preparing it, are already defcribed in 
fo many Books which treat of Hygrofcopes, that to 
mention them would feem unneceflary ; and I (hall 
only add, that lam 
Norwich, Dec. 21. 1745. 
Tours y See. 
« N 
Wm. Arderon. 
XIV. 
