r of uncertainty, as to the goodness of
the Instruments, by reason, that in _these_ the Air is, in some more, and
in some less perfectly excluded; whereas in _those_, that consideration has
no place. (And by the way, I have sometimes, upon this account, been able
to discover by our new Baroscope, that an esteem'd _Mercurial_ one, to
which I compared it, was not well freed from Air.) 6. It being, as I
formerly intimated, very possible to discover _Hydrostatically_, both the
bigness of the Buble, and the Contents of the cavity, and the weight and
dimensions of the Glassie substance (which together with the included Air
make up the Buble,) much may be discover'd by this Instrument, as to the
Weight of the Air, _absolute_ or _respective_. For, when the _Quick-silver_
in the _Mercurial_ Baroscope is either very high, or very low, or at a
middle station between its greatest and least height, bringing the
_Scale_-Barometer to an exact _AEquilibrium_ (1 with very minute divisions
of a Graine,) you may, by watchfully observing, when the _Mercury_ is risen
or faln just an inch, or a fourth, of half an inch &c. and putting in the
like minute divisions of a Grain to the lighter Scale, till you have again
brought the Ballance to an {238} exquisit _AEquilibrium_; you may, I say,
determine, What known weight in the _Statical_ Baroscope answers such
determinate Altitudes of the ascending and descending Quick-silver in the
_Mercurial_. And if the Ballance be accommodated with a divided Arch, or a
Wheel and Index, these Observations will assist you for the future to
determine readily, by seeing the inclination of the Cock or the degree
mark'd by the Index, what pollency the Buble hath, by the change of the
_Atmospheres_ weight, acquired or lost. Some Observations of this nature I
watchfully made, sometimes putting in a 64^{th.} sometimes a 32^{th.}
sometimes a 16^{th.} and sometimes heavier parts of a Grain, to the lighter
Scale. But one, that knew not, for what uses those little papers were,
coming to a window, where my Baroscopes stood, so unluckily shook them out
of the Scales, and confounded them, that he robb'd me of the opportunity of
making the nice Observations I intended, though I had the satisfaction of
seeing, that they were to be made. 7. By this _Statical_ Instrument we may
be assisted to compare the _Mercurial_ Baroscopes of _several_ places
(though never so distant) and to make some Estimates of the Gravities of
the Air there