_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.