Part 4

_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]]

PNEUMATICKS. 16

An Explication of the Second PLATE.

Figure 1. Is the Air-Pump, with its Receiver and Gage, as ready for Use; _a a_, _a a_ are two strong hollow Cylindrical Barrels, in which are suppos'd to be Suckers, with their Handles _c c_, _c c_ notched; into which Notches a Cog-wheel falls, which Cog-wheel moves upon the Axis _f_, when the Engine is put into Motion by the Winch _b b_. _g g_, _g g_ are two Cylinders of Wood, fixed to the Frame of the Air-Pump, with Screws at the Top, on which the Nuts _e_, _e e_ do run, and press down the upper Piece _f f_ upon the Tops of the Brass Barrels, to fix them both at Top and Bottom. _h h_ is a Swan-neck'd, or small bended hollow Brass Pipe, leading from the Top-Plate _i i i i_, or rather from the Brass hollow Piece above _n n_, which communicates through that Top-Plate with the Cavity of the Receiver. This Pipe is screwed to a bottom Brass Piece, included in the Box _d d_; which is perforated not only lengthways, but also upwards, in three Places: The Middle one for a Communication with this Swan-neck'd Pipe, and at the two Ends through small Cylinders; inserted into the two Brass Barrels _a a a a_; and 'tis by this Threefold Communication, that the Air is pump'd out of the Receiver. _l l l_ is the Gage; which is no other than a common Barometer, or Weather-Glass; with its Bason of Mercury _m m_, fix'd to the Engine by a particular Contrivance, and its Index or Boxen Receptacle, with Inches, and its Cork to support that Index upon the Surface of the Mercury, and to rise and fall with it; for the Exactness of measuring the Height of the Mercury from that Surface. Only this Barometer is open at the Top, and communicates, as does the Swan-neck'd Pipe, with the Cavity of the Receiver. _n n_ is a Stop-cock, that communicates also with the Cavity of the Receiver, and either excludes or readmits the Air, as you see convenient. _k_ is the Bottom of the Receiver, ground true to fit the Brass Circle below it; to which it is affixed by the Hand at first, and afterward by the Pressure of the Air, with wet Leather instead of Cement.

_Fig. 2._ Is a Barometer Tube, open at the Top H, and included in such a Receiver G B, as gives room for it to stand upright, and yet permits the Air to go backward or forward on its Surface, according as you pump the same out of or readmit the same into that Receiver. And this is done so, that the included Air C D, which supports the Mercury, by pressing on the Surface of that in its Bason E D, is confin'd within. This small Quantity of Air, on the Extraction of that in the Receiver, will, by its Elasticity, raise the Mercury almost as high as the usual Standard: And thereby shews, that the Spring of any small Part of common Air presses equally with the whole correspondent Column of the Atmosphere.

_Fig. 3._ Is a Contrivance to make an Explosion of Gunpowder in Vacuo: Where H D is a red hot Iron, standing on its Pedestal E, within a Receiver G C; and F is a Cock made above like a Dish, to contain the Gunpowder; which by the pulling up and thrusting down a strong Wire, with a Hole like the Eye of a Needle, is in a certain Quantity let fall every time upon the hot Iron; and on the Explosion produces Flame, and fictitious Air; but very little Sound, by reason of the Absence of the Air that should convey it.

_Fig. 4._ Is a Syringe, which will suck up the Water in the Glass C D, when it is in the open Air; but will not do the same under the Exhausted Receiver E F, unless for so small an Altitude as the remaining Air can sustain.

[[Plate III. ― I. Senex sculp.^t]]

PNEUMATICKS. 17

An Explication of the Third PLATE.

Figure 1. Is a large strong Glass Receiver, or Condenser, Arm'd with Brass Circles at both Ends, and fit to receive and bear the Pressure of Air considerably condens'd, when crouded into it by a Syringe fitted for that Purpose. It has also annexed to it a Gage C D, to determine the Quantity of the condens'd Air within. This Gage consists of a hollow Tube, Hermetically seal'd at D, with another smaller included, open towards D, and Hermetically seal'd at the other End. In this smaller Tube is left a little Quicksilver: This Quicksilver is by the Air at D in the larger Tube, which communicates with the condens'd Air in the Receiver it self, and so is of the same Density with it, crouded inwards towards C every time of the Admission of new Air; and by its whole Length from the End near D, compar'd with its Distance from the End near C, it determines the Proportion of the Density of the included Air to that of the common Air. _Note_, That the Syringe to be made use of with the Receiver, is the same with that represented in the next Figure, as joined to the condensing Engine it self; and acts by pulling up the Sucker above the Hole H, for the Admission of a full Cylinder of common Air, and then crouding it down into the Receiver; at the Bottom of this Syringe is a Valve, that hinders what is once crouded in from returning back again, as is necessary on all such Occasions.

_Fig. 2._ Is the usual Brass Condenser it self, with a Stop-cock E F near it; to be interposed between the Syringe and the Receiver upon Occasion. The Instrument, besides the Frame, is composed of a Recipient of Brass, made of Two Hemispheres, or what is equivalent to them, closed together by a Ring of wet Leather, to keep in the Air; and because in this Case the dense Air within endeavours forcibly to disjoin these Hemispheres, they are confin'd down close by a strong Piece of Iron, and Screws belonging thereto. The Syringe already describ'd, is represented as join'd to it after the same manner that it is when the Air is thereby intruded. This Brass Recipient will bear Air very much denser than the foregoing Glass one, tho' it being not transparent as the other is, cannot be so pleasant, nor so well shew the Mutations that happen to Animals or other Bodies in condens'd Air as the former.

_Fig. 3._ Is the Logarithmick Curve A C _c_, with its Ordinates A B, C D, _c d_, K δ representing Absolute Numbers, and its Abscissæ, C G or D B, I _c_ or B d and B δ, representing their Logarithms, whose famous Property it is, that one Ordinate as A B, is to another Ordinate as C D, or _c d_ or K δ, as that unlimited Space between the Curve and Asymptote above the one, is to that above the other; and whence is deduc'd the Proportion of the Air's Rarity at all Altitudes whatsoever; that at 7 Miles high it is 4 times as rare; at another 7, or 14 Miles, it is 16 times as rare, and so for ever, in a Geometrical Proportion of Rarity, compar'd with the Arithmetical Proportion of its Altitude; tho' all this is here upon the Hypothesis that the Distances are not so great, that the real Gravity of the Parts be sensibly diminished. For in that Case,

_Fig. 4._ Gives the Scheme, which is made use of to discover the Air's Rareness, even at such Distances, as imply a considerable Alteration in that Gravity; whence it will appear, that the Density of the Air is diminished in that Case more than 4 times for every 7 Miles of Altitude.

[[Plate IIII. ― I. Senex sculp.^t]]

PNEUMATICKS. 18

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:]]

PNEUMATICKS. 19

An Explication of the Fifth PLATE.

Figure 1. Are _Otto Guerick_'s Hemispheres, with their several Screws and Apparatus at large, set separately by themselves. They are designed to prove that the Force of the outward Air, when the inward is extracted from between them, is equal to the Weight of a Column of Quicksilver of about 29 Inches and a half: Of Water of about 34 Feet: And of Air to the Top of the Atmosphere, all pressing upon the same Base with the largest Circles of those Hemispheres.

_Fig. 2._ Is the Syringe, with its Hole; to be screw'd on to the Top of the Receiver of the next Figure; in order to thrust Air into it, for the Improvement of the former Experiment; or to shew that tho' common Air be left in the Hemispheres, yet if that on their outward Surface be made twice or thrice as dense, they will still sustain an equal, or a double Weight respectively, before they are separated.

_Fig. 3._ Is that Instrument included in such a Receiver D B, and that Receiver kept close to its Basis by a cross Piece and Screws, as in the Condenser before: Together with a newly contriv'd Stiliard, to which the upper Hemisphere is hung; with its fixed Base, and its Gage, to measure the Degrees of Condensation of the Air, where by the Proportion of S P to P K, the Weight 50 w. is equivalent to greater Weights, and shews how many Pounds are required to separate the Hemispheres in all Cases. If the Diameter be 3 Inches and a half, they will sustain about 150 Pounds; and so in all other Proportions.

_Fig. 4._ Is the Plate which covers the upper Part of the Receiver. And through the Hole C the Piece D E slides, which takes hold on the upper Hemisphere.

_Fig. 5._ Shews the Gage of the same Instrument; this is like that for the Glass Condenser before describ'd, and contains a bended Tube, whose open End is in a small Basin of Mercury; and the other is Hermetically seal'd: For this Mercury crowded by the condensed Air in the Receiver, will croud the Air in the small Tube closer in Proportion to its Density, and so will afford us the Knowledge of the Quantity thereof.

_Fig. 6._ Is a like Experiment of the Cohesion of polished Plates of Brass, or of Marble; when the Air is excluded by a little Oil, and an exact Application. This Cohesion may be weighed by the Stiliard, as well as that of the Hemispheres; and is equal to the same, upon the same Base; provided a Ring do prevent their side or sliding Motion; and provided the Air can equally be excluded from between the Plates, as between the Hemispheres. Which last yet is almost impossible to be done.

_Fig. 7._ Is a Number of great Weights, kept steady one over another by an Iron Rod passing through them, and pressing upon a Bladder half blown, plac'd below them: This Bladder, by the Elasticity of its included Air, gradually elevates all those Weights; as soon as by the Extraction of the other Air out of the Receiver, wherein they are all included, its Counterpoise is gradually taken away.

_Fig. 8._ Is a Number of Jet d'Eaus, or Fountains, made by condens'd Air, in a large Copper Vessel C D, pressing on the Surface of Water at the Bottom of the Vessel; into which Water a hollow Brass Pipe is immers'd. For if there be then a Stopcock at G, to open or shut the hollow Pipe at Pleasure; and several smaller Pipes at I K, communicating therewith, turning upon Balls or Joints, and plac'd in Order, we shall have a very pleasant Set of these _Jet d'Eaus_, or Fountains; all whose Water will be caught by the Bason A B, which Water may be again let into the Vessel C D, by unscrewing the Pillar in the Center of the Bason.

[[Plate VI. ― I. Senex sculp.^t]]

PNEUMATICKS. 20

An Explication of the Sixth PLATE.

This Plate is in Reality but one compound Instrument or Apparatus, for trying the Electricity of Glass, and its Luminousness, when put into Motion, and rubb'd upon to heat it. Wherein B C is a Wheel, with its String A B C. D E is a Sphere of Glass, whose Air has been drawn out by the Air-Pump: This is turned round by the former Wheel-string at A. F is a Stopcock, whereby the Air is exhausted, and may be readmitted at Discretion.

In _Fig. 1._ K L M is an Arch with Threads of Cruel or Yarn upon it, as they hang about the Glass D E, (here represented by a smaller Circle within the Arch) before it is turned round or heated by rubbing.

_Fig. 2._ G H I is the same with the former; only the Threads are here represented as they hang at the Beginning of the turning round of the Globe, before it be heated by Friction; being plainly bent one way, by a Wind arising from that Convolution.

_Fig. 3._ N P O is the same; only with the Threads pointing towards the Sphere, or its Center, when the Arch is in an upright Posture, and some of the Threads hang partly downwards, and this upon the Spheres being heated sufficiently.

_Fig. 4._ Q S R is the same, with its Threads pointing the same way, though in a downward Posture, when some of the Threads thereby are forc'd to stand erect.

_Fig. 5._ T U is a Circular Arch, in an horizontal Position, when the Threads point towards the same Center, in the same horizontal Plain.

_Fig. 6._ Is another Sphere, communicating with the Air, and to be apply'd to the same Wheel in the Room of D E, where-into is inserted an Axis with a Circle affixed to it; at the Edges of which Circle the Threads are placed. These upon the Friction and Heat of the Glass extend themselves outward, and point from the Center to the Circumference, contrary to the former. In both Cases the Threads, when under the Influence of the Electricity, will be moved by the Finger, even without Contact, nay by the Finger and Breath, even through the Glass it self; so subtle are these _Effluvia_. The Light is made when the Air is exhausted, and diminishes as you readmit it. It spreads and branches it self inwardly like Lightning, when about half that Air is readmitted. The Colour of that Light is always Purple. It spreads at some Distance, and makes the Edges of a Cravat look a little like the milky Way, by the great Number of Sparkles it emits: Which may also be felt by the Flesh, with a crackling Noise that accompanies them. If you also sufficiently rub and heat a large Tube of Glass, either solid or hollow, it becomes strongly Electrical, even through Glass it self; tho' not so much through Muslin. Other Heat than that by Friction signifies nothing. It will attract and repel Leaf Gold, and the like small and light Bodies, after a strange manner, by turns; when once they have been fully repell'd they cannot be made to touch them, till they have been reflected from some other Body. If they lye between two Pieces of Wood, laid pretty near, the Electricity fails of its Effect. With other Circumstances very surprizing and unaccountable.

_FINIS._

Transcription note:

The original punctuation and ortography of the book have been faithfully preserved; words which are spelled variantly, or inconsistently capitalized (e.g., _Axel_ vs. _Axle_, _crowded_ vs. _crouded_, _blue, red_ vs. _Blue, Red_, etc.) have been left as such.

Likewise, the (mis)spelling of names like Galilæo, Azout, Hugen, Guerick, has been retained.

The following typographical mistakes have been corrected, taking into account recurrences across the text:

* Page III, 25th day: * The Ebullition of Liquors in _Vacuo_ → The Ebullition of Liquors _in Vacuo_

* Mechanicks, Explication of the 2nd Plate: * Figure. 1. Is the deceitful Balance; which yet is _in Equilibrio_ → Figure 1. Is the deceitful Balance; which yet is _in Æquilibrio_ * _Fig. 3_ → Fig. 3. * [Fig. 10]: perpendiculary → perpendicularly * [between Fig. 9 and 10]: N. _B._ → _N. B._ * [Fig. 10]: and in this Leaver → and in this Lever

* Mechanicks, Expl. 5th Plate, Fig. 3: * us it is less restrained. → as it is less restrained.

* Opticks, Expl. 1st Plate, Fig. 3: * Looking-glass → Looking-Glass

* Opticks, Expl. 2nd Plate: * _Fig. 8._ Shows → _Fig. 8._ Shews * [Fig. 10]: on the like Acccount. → on the like Account.

* Hydrostaticks, Expl. 1st Plate: * [Fig. 5]: specifick Gravity of Water → Specifick Gravity of Water

* Hydrostaticks, Table of Specifick Gravities: * Spirit of Nirre → Spirit of Nitre

* Pneumaticks, Expl. 2nd Plate: * [Fig. 1]: 'tis by this Thteefold → 'tis by this Threefold * [Fig. 2]: small Part of ccmmon Air → small Part of common Air

* Pneumaticks, Expl. 5th Plate: * [Fig. 6]: as between the Hemispheres → as between the Hemispheres.

* Pneumaticks, Expl. 6th Plate: * [Fig. 6]: througn Muslin → through Muslin