An Explication of the Fourth PLATE.
Figure 1. Is a compound Instrument, to shew, why in a Storm the Mercury in
the Barometer vibrates so much, by a parallel Case in an Imitation of such
a Storm. A A is a large hollow Brass Sphere, into which by the means of
the Syringe in _Fig. 2_. Air is crouded till it is 8 or 10 times as dense
as usual. H F and L K are Two Barometers, with their Basons in the Boxes
F F, K K, which Boxes communicate by a long hollow Tube I I. E E is a
Brass hollow Tube, to convey the crowded Air near the Surface of one of
the Basons of Quicksilver, which Air passes out of that into a larger
hollow Pipe G G, and so into the open Air. Upon the turning of the
Stopcock C to give vent to the condensed Air, it rushes with great Force
along the hollow Pipes E E, G G; and as it passes not far off the Surface
of the Bason of Quicksilver F F, it causes the Mercury in both the
Barometers H H, and L L, to descend and vibrate several Inches, as the
great Storm made Barometers descend and vibrate in Chambers at a distance
from it.
_Fig. 3._ Is a Transferrer; containing one common hollow Stem I (here
represented as screw'd to a square Piece of Wood, and thereby held
upright) with its Stopcock I, and its Horizontal Hollow G H with which it
communicates. Upon this Horizontal Piece two more hollow Stems are
erected, and communicate therewith. These also have Stopcocks E and F, and
to these are screw'd Two Brass Plates A B and C D, on which Two Recipients
may be fix'd, and may communicate with the rest. By this means the whole
Instrument may be apply'd to the Air Pump, and one or more of its
Recipients exhausted; and afterward any Factitious or Natural Air may be
transferr'd from one Receiver to another, as Occasion requires: Of which
Instrument Mr. _Boyle_ made great Use in his Second Continuation of
Experiments.
_Fig. 4._ Are very small or capillary Glass Tubes, of different Bores, let
down into Tinged Water, in Vacuo, to shew, that by the Attraction of the
Glass the Water will be elevated, contrary to the ordinary Law of
Hydrostaticks, and that to a considerable Height; and what is chiefly
remarkable, is, that the Altitude of the Liquid in the Tubes is the same
in Vacuo as in the open Air, and is always in an exact reciprocal
Proportion to the Diameters of their Bases.
_Fig. 5._ Is the noble Improvement of the former Experiment by Mr.
_Hauksbee, Sen._ upon which the Learned Mr. _Ditton_ has written a small
Treatise. It is done by two Glass Plains, A C B, A D B, meeting in an Axis
at A B; and being about a Tenth of an Inch distant at the greatest
Aperture D C. These Plains are Erected in Spirit of Wine, and are like a
Series of Tubes of all different Diameters less than D C, which must
therefore elevate the Fluid a little at D C, and higher all the way to B,
where the Elevation ought to be Infinite; the Tops of the elevated Columns
will form an Hyperbola, E F G, with its Two Asymptotes, the Surface of the
Fluid D C B, and the Line B A. _Note_, That if the Angle at D C be
altered, the Bigness of the Hyperbola will be alter'd, while its Species
remains; but that if the Angle A B C be alter'd, the Species of the
Hyperbola will be alter'd also, though it will still be a true Hyperbola,
and that if the Glass be clean, to a surprizing Degree of Exactness.
[[Plate V. ― Sutton Nicholls sculp:]]