367

Nouember the 27. 1679

Sr. Christopher Wren the Vice Pt. tooke the chair

The minutes of Nouember the 20th. were read, wherevpon
It was further Discoursed Debated whence the Grauity /alteration of the/ grauity of
the Air Proceeded. whether from the Greater height of the air
by add a new Influx of Air from some other Part of
world, whereby the perpendicular altitude was increased
or Diminished and consequently the pressure or from the
neer accession of steames fumes or saline substances Dissolud
and taken vp by the air, in the manner as Aquafortis takes
vp into its self Siluer Copper Iron &c. and soe is made
heauier in Specie then it was before it was soe Impreg
nated, and thus though it were not Increased in Bulk or
height yet it might be increased in Grauitation & pressure
mr. Hooke was of opinion that both these causes might concurr
to produce this Effect, and that in order to the examination
thereof he had contriued two kinds of Barometers, which
were first mentiond to this society as he conceiued about
the year 1662, and Lately also vizt this Last year. The first
of wch. should only shew the variations of the Pressure of
the Air caused by the alteration of the pressure of the air
from either or both causes. But the second should only -
shew the alteration of the pressure of the air from the
alteration of the specifick Grauity. Sr.
Sr. Christopher wren was of opinion that it Did most of
All proceed from the impregnating of the air by the nitrous
salts. which were continually Raised vp into it.
Dr. Croon mentiond that Dr. Grew had formerly brought in
an account of the solutions of salts by water which would
serue to Explaine this notion which he conceiud 'twould be well
to consult.
mr. Hooke alledged he had about 8 years since shewn the Society
an Experiment at Arundell house to proue the penetration of liquid
one into another by putting oyle of vitrioll into water in a bolthead
. . . . . . . .

Ref: CELL/RS/HF_369  © Centre for Editing Lives and Letters