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 DB, 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 SP to PK, 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 DE 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 CD, 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 IK, 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 AB, which Water may be again let into the Vessel CD, by unscrewing the Pillar in the Center of the Bason.