( 640 ) 
The Method of doing which Operation was by means 
of a large Poife of Ghls, fomewhat of the fhape of a 
Bolt-head, the Bali of which was about 3 Inches Dia- 
meter, but the Seem or Neck thereof was not above half 
a Line, or a twenty fourth part of an Inch- this was fo 
poifed by Red Lead put into it, as to make it but a lit- 
tle heavier than fair, or frelh Water. Then this Poife 
was fufpended by the fmall Stem to the end of a (lender 
Beam, which was very tender, and being not over- char- 
ged with weight, would turn with a (mall part of a 
Grain. This Beam was hung on a fteady Frame, and 
the Poife hanging at one end of the fame, cover'd with 
the Water to a certain Mark or Divifion made on the 
fmall Neck, it was fb counterpoifed by fome fmall 
Weights put into the oppofite Scale of the Ballance. 
Then (the weight of the Water contained in the Cittern 
or Veflel into which the Poife was immerfed being firft 
known) a 2000 th part of it's weight was taken ot com- 
mon Salt weighed out,and put into the whole 2000 parts 
of the Water, which by being ftirred (bon diflblved. Then 
the Poife fufpended as before, was viewed and examined 
by many then prefent, and they manifeftly faw that 
near half an inch more of the Neck emerged out of the 
Water fo feafoned, than did before the 2000 th part of 
Salt was diflblved therein, This was only one ufe of 
this Method of difeovering very fmall Alterations in 
the Confiitutions of Bodies, the fame Author having 
long fince, namely, Ottober z$. 1677. (hewn to the fame 
Society a Method of difeovering divers Alterations much 
more curious, namely, to the 1 76000 th part of it s 
weight. 
This Defcription will be more eafily apprehended by 
the firft Figure, where A fignifies the Beam, B the Ball 
of the Poife, CC the Neck, D the Mark to which it funk 
in 
