163

Feb: 21. 1677/8

Sr. Iohn Hoskins tooke the chair
The minutes of the 14 instant were Read, and by the way vpon the mention
of the Hornets nest Sr. Iohn Hoskins mentiond that mr. wheeler had seen the way
of Beehiues -


mr. George Ent Presented the Society for their Library the new Pharmaecopea
Londinensis reprinted and amended by the care of his father Sr. George Ent
He receiud the thanks of the society for this present & the booke was deliuerd
to mr Hunt for the Library.

mr. Hooke produced an Instrument to examine and shew at all times the specifyck
grauity of the air in wch. it is placed, wthout any respect to the heat or cold
pressure or spring of the air, but said property of the air is not shewd singly
by any other Instrument, nor is it proper ^ /or capable/ to shew any other quality of the
air ^ /as some haue thought/ saue only the specifique grauity thereof. This Intrument was first pro
pounded by him to this Society in the year      and remaines vpon the regis=
ter book but ^ /the experiment & the Instrument it self/ was not before this exhibited at these meetings. -

The present instrument made to Demonsrate the said propriety was a very
large and thin ball of Glasse sealed vp hermetically. this was suspended at the
end of an exact beam (which would easily turne either one way or the other) and was
counterpoised by a small weight of Lead or brasse but Lead was best for that
purpose, then mr Hooke explaind the same and shewd the reason why the
said ball would rise when the air in wch. it hung was heauier and sink when
it was lighter and depended vpon the same ground wth the Improuement of Archi
medes Expt. by Ghetaldus. he also explaind the Difference between the pressure
and the specifique grauity of the air. whereupon Sr. Iohn Hoskins added that
this was properly the Barometer and not the other instrument soe called.
Sr. Iohn Louther Demanding whether this Instrument now produced were curious enough
to make the small mutations in the air visible, mr. Hooke answered that he did
not exhibit this for any other vse saue only to shew the ground and Reason
of the thing, and as a sensible obiect vpon wch. to reason and discourse
wherevpon and for the more plaine demonstration and explanation of all
materiall doubts that might arise because wthout such a subiect, pattern
or module of the thing designed, the propounder of such experiment or
Inuention is for the most part not soe readily vnderstood & very often mis
taken or misapprehended by the auditors. nor can obiections be pertinent
ly made where the like module is wanting especially in all mechanicall subiects

Ref: CELL/RS/HF_165  © Centre for Editing Lives and Letters