m Depth at Top, but gradually widening towards 
the Bottom, with a Back to Hide up and down in a 
Groove. The Axis, already mentioned, of an Inch. 
Length, came through a Hole in the Front of the Box, 
and then had the Index faftened on, which de- 
lcribcd the Segment of a Circle upon a brafs Plate, 
itlver’d and graduated into 180 Gr. as if it had con- 
lifted of a perfed Semicircle , or two Quadrants. The 
Reafon why the Graduation did not begin exactly with 
the diametrical Line was, to prevent the Fri&ion of 
the Brachia of the Balance, with the little Drop 
placed at the Bottom of the Axis already mentioned. 
My next Concern was to charge this Balance. The 
Beam turned, as has been laid, with half a Grain ; 
and every fuch Turn, after repeated Trials, moved 
the Index fomewhat more than one ^Degree of the 
1 So deferibed upon the Plate ; fo I immediately 
pitched upon a Four Peny-weight all but fix Grains , 
which contained as many half Grains as there were 
i Degrees . This Weight I fixed with a Thread to one 
Brachium of the Balance , without any Scale , the fe- 
veral Threads or Silk Strings of which, as they would 
imbibe more Moifture, would make the Machine lefs 
accurate; and the other Brachium I charged with a 
Sponge , fufpended likewife by a Thread, of fuch a 
Weight, when reduced to absolute Drynefs, as made 
an Equilibrium ; and then ferewing on the Index to 
the firft Degree of the 180, and expoftng the Ma- 
chine, thus ordered, to the open Air , in one Night’s 
time the Index had got to the 70th Degree ; which, 
as the Sponge had been abfolutely dry, muft have 
been the true State of the Air , as to Moifiure , at 
that time. 
I find 
