consequently,
that since it appear'd by the _Baroscope_, that the weight of the Air was
sometimes heavier, and sometimes lighter, the alterations of it, in point
of gravity, from the weight, it was off at first counterpoising of the
Buble of it, would _unequally_ affect so large and hollow a Body, as the
Buble, and so small and dense a one, as a Metallin weight: And when the Air
by an increase of gravity should become a heavier _Medium_, than before, it
would buoy up the Glass more than the Counterpoise; and if it grew lighter,
than it was at first, would suffer the former to preponderate: (The
Illustrations and Proof can scarce be added in few words; but, if it be
desired, I may, God permitting, send you them at my next leasure:) And
though our English Air be about a thousand times lighter, than water, the
difference in weight of so little Air, as is but equal in bulk to a Buble,
seem'd to give small hopes, that it would be sensible upon a Ballance; yet,
by making the Buble very large and light, I supposed and found the Event, I
have already related.

_Secondly_, The hermetically seal'd Glass-buble, I employed, was of the
bigness of a somewhat large _Orange_, and weigh'd about 1. drachme and 10.
grains. But I thought it very possible, if I had been better furnish'd with
conveniencies (wherein I afterwards found, I was not mistaken) to make
(among many, that might be expected to miscarry) some, that might be
preferable to this, either for capacity or lightness, or both; especially
if care be taken, that they be not seal'd up, whilst they are too hot. For,
though one would think, that it were {235} advantagious to rarify and drive
out the Air as much as is possible, because in such seal'd Bubles the Air
it self (as I have elsewhere shewn) has a weight; yet this advantage
countervails not the inconvenience of being obliged to increase the weight
of the Glass, which when it includes highly rarified Air, if it be not
somewhat strong, will be broken by the pressure of the External Air, as I
have sufficiently tryed.

_Thirdly_, I would have tryed, whether the _Dryness_ and _Moisture_ of the
Air would in any measure have alter'd the weight of the Buble, as well as
the Variation of Gravity produced in the _Atmosphere_ by other causes; but
the extraordinarily constant absence of Fogs, kept me from making
Observations of this kind; save that one morning early, being told of a
mist, I sent to see (being my self in bed) whether it