Single Cane, or have a round Bolthead at the
top. And by the means thereof, the {219} Variation of the Altitude of the
_Mercurial_ Cylinder, which at most is hardly three Inches, may be made as
distinguishable, as if it were three Foot, or three Yards, or as much more,
as is desired.

The manner hereof is visible enough by _Figure_ I: where A B C represents
the Tube, which may be either Blunt, or with a Head, as A B C (by which
latter shape, more room is allow'd for any remainder of Air, to expand the
better.) This is to be filled with Quick-silver, and inverted as commonly;
but into a Vessel of Stagnant Mercury, made after the fashion of I K, that
is, having its sides about 3 or 4 inches high, and the Cavity of it equally
big both above and below; and if it can be (besides that part, which is
fill'd by the end of the _Mercurial_ Tube, that stands in it) of equal
capacity with the hollow of the Cane about B: For then the Quicksilver
rising as much in the hollow of I, as it descends at B, the difference of
the height in the Receiver I, will be just half the usual difference, And
if the receiving Vessel I K have a bigger Cavity, the difference will be
less, but if less, the difference will be greater: But, whether the
difference be hereby made bigger or less, 'tis no great matter, since by
the contrivance of the _Wheel_ and _Index_ (which is more fully described
in the _Preface_ to the _Micrography_) the least variation may be made as
sensible as is desired, by diminishing the bigness of the Cylinder E, and
lengthening the _Index_ F G, according to the Proportion requisite.

* * * * *

_An Account of _Four Suns_, which very lately appear'd in _France_, and of
two _Raine-bows_, unusually posited, seen in the same Kingdom, somewhat
longer agoe._

These _Phaenomena_ are thought worthy to be inserted here, for the
Speculation of the Curious in those Kingdoms; as they were publisht in the
French _Journal des Scavans_, of May 10, 1666. _viz._

The 9th of _April_ of this present year, about half an hour past nine,
there appear'd three Circles in the Sky. _One_ of them was very great, a
little interrupted, and white every where, without {220} the mixture of any
other colour. It passed through the midst of the Sun's _Disk_, and was
parallel to the _Horizon_. Its _Diameter_ was above a hundred degrees, and
its _Center_ not far from the _Zenith_.

The _Second_ was much less and defective in some p