Air-Pumps, or Engines for Exhausting the Air from proper Vessels, with all their Appurtenances; whereby the various Properties and Uses of that Fluid are discover'd and demonstrated by undeniable Experiments. Engines for the Compression of the Air: Fountains, in which the Water, or other Liquor, is made to ascend by the Force of the Air's Spring. Syringes and Blow-Pipes, with Valves for Anatomical Injections. Hydrostatical Balances, for determining the Specifick Gravity of Fluids and Solids. The Engine and Glasses for the New Way of Cupping without Fire. Scarificators, which at once make either 10, 13, or 16 Incisions. Weather-Glasses of all Sorts, as Barometers, Thermometers, _&c._ Reflecting Telescopes, by which in so short a Length as Six Feet, all that has hitherto been discovered in the Heavens (by the longest Telescopes of the common Construction) may be observed. All the above-mention'd Instruments, according to their Latest and Best Improvements, are made and sold by FRANCIS HAUKSBEE, in _Crane-Court_ in _Fleetstreet, London_. [[Mechanicks Plate I. ― Sutton Nicholls sculp:]] 1 MECHANICKS. An Explication of the First PLATE. Figure. 1. This belongs to _Galilæo's_ famous Demonstration of the Velocities and Times of Bodies descending by an uniform Force, such is that of Gravity here below: And shews that they will ever fall in equal Times, 1, 2, 3, 4, _&c._ according to the odd Numbers, 1, 3, 5, 7, _&c._ or the Trapezia B C D E, D E F G, F G H I, _&c._ and by consequence, that their Velocity will increase uniformly in Proportion to the Lines B C, D E, F G, H I, _&c._ or to the Times of Descent. And that the entire Lines of their Descent will be as the Triangles A B C, A D E, A F G, A H I, _&c._ or as the Squares of those Times, 1, 4, 9, 16, _&c._ _Fig. 2._ This is a strong Balance for an Experiment to prove the former Proposition, by shewing that any Bullet or Ball, when it falls from four Times the Height, has twice, from nine Times the Height has thrice its former Velocity or Force; and will accordingly raise a double or triple Weight in the opposite Scale, to the same Height, and no more; and so for ever. _Fig. 3._ This shews how Bodies upon an inclin'd Plane will _slide_, if the Perpendicular through the Center of their Gravity falls _within_; and will _rowl_, if that Perpendicular fall _without_ their common Section. _Fig. 4._ This shews that an oblique Body will stand, if the Perpendicular through its Center of Gravity cut the Base; and that it will fall, if it cut not the Base: As accordingly we stand when the Perpendicular through the Center of Gravity of our Bodies falls within the Base of our Feet; and we are ready to tumble when it falls without the same.