A Course of Mechanical, Magnetical, Optical, Hydrostatical and Pneumatical Experiments / perform'd by Francis Hauksbee, and the Explanatory Lectures read by William Whiston, M.A.

by William Whiston; Francis Hauksbee

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.

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.