A TABLE of the Specifick Gravities of several Solid and Fluid Bodies.
Fine Gold 19,640 Calculus Humanus 1,700
Standard Gold 18,888 Oyl of Vitriol 1,700
Quicksilver 14,000 Oyl of Tartar 1,550
Lead 11,325 Bezoar 1,500
Fine Silver 11,091 Honey 1,450
Standard Silver 10,535 Gum Arabick 1,375
Bismuth 9,700 Spirit of Nitre 1,315
Copper 9,000 Aqua Fortis 1,300
Cast Brass 8,000 Serum of Human Blood 1,190
Steel } Soft 7,738 Pitch 1,150
the same } Hard 7,704 Spirit of Salt 1,130
Piece } Spring Temper 7,809 Spirit of Urine 1,120
Iron 7,645 Human Blood 1,040
Tin 7,320 Amber 1,040
Glass of Antimony 5,280 Milk 1,030
A Pseudo Topaz 4,270 Urine 1,030
A Diamond 3,400 Dry Box-Wood 1,030
Clear Crystal Glass 3,150 Sea-Water 1,030
Iceland Crystal 2,720 Common Water 1,000
Fine Marble 2,700 Camphire 0,996
Rock Crystal 2,650 Bees-Wax 0,955
Common Green Glass 2,620 Lynseed Oyl 0,932
Stone of a mean Gravity 2,500 Dry Oak 0,925
Sal Gemmæ 2,143 Oyl Olive 0,913
Brick 2,000 Spirit of Turpentine 0,874
Nitre 1,900 Rectified Spirit of Wine 0,866
Alabaster 1,875 Dry Ash 0,800
Dry Ivory 1,825 Dry Maple 0,755
Brimstone 1,800 Dry Elm 0,600
_Dantzick_ Vitriol 1,715 Dry Firr 0,550
Allom 1,714 Cork 0,240
Borax 1,714 Air 0,001 ¼
[[Plate I. Pneumaticks]]
15
PNEUMATICKS.
An Explication of the First PLATE.
Figure 1. Are several Torricellian Tubes or Barometers of different
Shapes, Bores, and Positions; but where the perpendicular Altitude of the
Quicksilver in the Tubes, above the Level of the Surface of that in the
Bason, is ever the same, or between 28 and 31 inches high; which is the
known Counterpoise between 32 and 36 Feet of Water; and to the entire
Atmosphere in its several States and Elevations, where the Bases or the
several Tubes are supposed equal.
_Fig. 2._ Is a Diagonal Barometer, where the Alteration of the
Perpendicular Altitude of 3 Inches, by the Obliquity of that Part B C of
the Tube A B C, (as a Diagonal is oblique to the Sides of its
Parallelogram,) is increas'd to 20 or 30 Inches Sideways, for more Nicety
of Observation.
_Fig. 3._ Is a Wheel Barometer, where by two Weights G and H on a Pulley,
by which a Hand is turned, the one of which plays freely in the Air, and
the other rises and falls with the Quicksilver in the Tube, the Divisions
are larger and more obvious than in the ordinary Barometer: as they are in
the Diagonal one; for the like greater Nicety of Observation.
_Fig. 4._ Is a common Thermometer, to determine the Quantity of the Heat
of the Air, or of any Liquor, by the Rarefraction of Spirit of Wine
contain'd in the hollow Ball at the Bottom, and its consequent ascending
to the several Divisions on the small Tube.
_Fig. 5_, and _12_. Are to shew that the Air's Density is as its
Compression, the former upon a greater Compression, and the latter upon a
greater Rarefraction; and that accordingly, in the first Case, B D the
Standard Altitude, or about 29½ Inches, and L M the Additional Altitude of
Quicksilver pour'd in higher than the Level H, taken together, is to B D
the Standard Altitude alone, as I G the inverted Part of the Tube when
full of common Air, to H G the Part full of condens'd Air: And in the
Second Case, B D the Standard Altitude, is to D C the Depression by the
Air, as E C the Part of the Tube full of the expanded Air, to E F the Part
at first left full of common Air.
_Fig. 6._ Is Monsieur _Azout_'s noble Experiment, to determine, that 'tis
certainly the Air's Pressure that raises the Quicksilver in the Barometer.
The Instrument is nothing but a double Barometer communicating together,
by the Means of a small hollow Pipe in the Middle: Its lower Tube is
stopp'd at the Bottom with a Bladder; and when the entire Cavities are
full of Quicksilver, the Bladder is prick'd or cut, and the Quicksilver
runs out: Hereupon the upper Barometer's Tube, and Part of its Bason,
becomes empty; while the lower is yet full: But upon the unscrewing a
Screw, and letting Air in above the upper Bason, that Air presses on the
Quicksilver's Surface, and raises it into its Tube; while the same Air
pressing down the upper Part of the under Tube, depresses the Quicksilver
therein at the same time.
_Fig. 7._ Is a Hygrometer, or Cord, with a Needle or Index in a Circle, to
measure the Air's Moisture by its shrinking up, and consequent Revolution
one way; and the Air's Dryness, by its Extension down, and consequent
Revolution the contrary way; and both measured by the Degrees of the
Bottom Circle.
_Fig. 8._ Is a Syphon above 29½ Inches high, along where no Suction nor
Art can make the Quicksilver run, as it uses to do when it is of any less
Altitude.
_Fig. 9._ Is the new Sort of Cupping-Glass, whence the Air is suck'd out
by a Syringe, and where by a Valve it is hindred from returning.
_Fig. 10._ Is an Example of Suction; and will shew that Quicksilver can
thereby never be rais'd to 29½ Inches.
_Fig. 11._ Is an Example of a Weight raised by a Syringe, as Water uses to
be; and still shews, that all is proportionable to the Power of the Air's
Pressure, and is limited thereby.
[[Plate II. ― I. Senex sculp.^t]]