167
[In margin]Vol. 4.
Feb: 28. 1677/8.
m
r. Henshaw the vice president tooke the chair.
Then m
r Hooke Read the minutes of the la
st meeting after w
ch.
In prosecution of w
t. was de
sired the La
st day m
r. Hooke shewd An experiment
further to Elucidate the theory of the Air poi
se produced the Day
before namely to proue that a
ball of large & very light ball of
gla
sse orderd as it was the la
st would, vpon the change of the
specifique grauity of the fluid in w
ch. it was suspended, ri
se
and fall w
th. such a motion as would make such alteration
se
sib[le]
In order to w
ch. becau
se such alteration were hard to make in the Air
and
but becau
se the la
st in
strument was only de
signed to shew
the gro
sse mutations and not the minute ones he hauing as he
affirmed an other way differing from w
t was exhibited for produ
cing the Effect w
ch. would be somew
t more chargable to produce.
therefore a gla
sse sealed vp as in the former experiment was
sealdvp su
spended at the end of a beam and both that a counterpoi
se to it
when both vnder the water were hung into a ve
ssell of fair water
which was
. . . taken notice of. Then into that water was put
a small quantity of salt that soe by the Di
ssolution thereof the watermight be made heauier in Specie, and thereby the bigger body w
ch. was
the sealed gla
sse might be made lighter than its counterpoise
. . .euery ^ /new/ fluid taking off soe much /more or le
sse/ of the weight of the body conteined in
it ^ /then was taken off by a former fluid/
the weight of as a quantity of it aequall in bulk to the said contein
ed body doth weigh heauier ^ /or lighter than
the like quantity of the/
than the fluid in w
ch. it was la
st suspended
. . . Wherevpon it was immediately very manife
stly verifyd for the gla
sse
ball immediately vpon the putting in of the salt Grew very se
sibly light
er and the counterpoi
se preponderated. where by all the obiections and
scruples that were made concerning the former theory were remoued
And when Inquiry was made whether it coud not be ordered soe as to make
the minute variations more sen
sible m
r. Hooke affirmed that he had
a way by w
ch. he could make them as se
sible as should be De
sired
& that in steed of varying an inch he could make it vary 10, 20 or more
feet. the only inconuenience of w
ch. In
strument was Du
st becau
se
that settling vpon the superficier of the Gla
sse would augment the
weight
of thereof, but for preuention hereof He said a gla
sse -
couer and ca
se might be soe orderd as to preuent all tho
se incon
ueniences and yet not at all hinder the air w
thin it from being sesible
and compatible of the air w
thout in the Room in w
ch. it was placed -
Ref: CELL/RS/HF_169 © Centre for Editing Lives and Letters
