e a square
Lanthorn with Glass-windows, and a hole at the top for the Commerce of the
internal and external Air, will be more free from dust, and irregular
agitations; to the latter of which, it will otherwise be sometimes
incident.

_Sixthly_, This instrument being accommodated with a light Wheele and an
Index (such as have been applyed by the excellent Dr. _Chr. Wren_ to open
Weather glasses, and by the ingenious Mr. _Hook_ to _Baroscopes_) may be
made to shew much more minute variations, than otherwise.

_Seventhly_, And the length of the Beam, and exquisitness of the Ballance,
may easily, _without_ any of the foregoing helps (and much more _with_
them) make the instrument far exacter, than any of those, I was reduced to
employ. And to these Accommodations divers others may be suggested by a
farther consideration of the nature of the thing, and a longer practice.

Though in some respects this _Statical_ Baroscope be inferior to the
_Mercurial_; yet in others it has its own advantages and conveniencies
above it.

And 1: It confirms _ad oculum_ our former Doctrine, that the falling and
rising of the _Mercury_ depends upon the varying weight of the Atmosphere;
since in this Baroscope it cannot {237} be pretended, that a _Fuga vacui_,
or a _Funiculus_, is the cause of the changes, we observe. 2. It shews,
that not only the Air has weight, but a more considerable one, than some
Learned men, who will allow me to have prov'd, it has some weight, will
admit; since even the variation of weight in so small a quantity of Air, as
is but equal in bulk to an _Orange_, is manifestly discoverable upon such
Balances, as are none of the nicest. 3. This _Statical_ Baroscope will
oftentimes be more parable, than the other: For many will finde it more
easie, to procure a good pair of Gold-scales, and a Buble or two, than a
long Cane seal'd, a quantity of _Quick-silver_, and all the other requisits
of the _Mercurial_ Baroscope; especially if we comprise the trouble and
skill, that is requisite to free the deserted part of the Tube from Air. 4.
And whereas the difficulty of removing the _Mercurial_ Instrument has kept
men from so much as attempting to do it, even to neighbouring places; the
Essential parts of the _Scale_-Baroscope (for the Frame is none of them)
may very easily in a little room be carried, whither one will, without the
hazard of being spoil'd or injur'd. 5. There is not in _Statical_
Baroscopes, as in the other, a dange