A continuation of new experiments physico-mechanical, touching the spring and weight of the air and their effects. The I. part whereto is annext a short discourse of the atmospheres of consistent bodies / written by way of letter to the right honourable the Lord Clifford and Dungarvan by the honourable Robert Boyle ...

EXPERIMENT V.

About a way of speedily breaking Flat Glasses, by the weight of the Atmosphere.

FOr the more easie understanding of some of the subsequent Tryals, it will be requisite in this place to mention among Experiments about the Spring of the Air the following Phaeno∣menon belonging to its Weight.

This is one of those that is the most usually shown to Stran∣gers, as a plain and easie proof both that the Weight of the in∣cumbent Air is considerable, and that the round figure of a Re∣ceiver doth much more conduce to make an exhausted Glass sup∣port that weight, than if the upper part of the Receiver were flat.

To make this Experiment we provided a Hoop or Ring of Brass of a considerable thickness, whose height was 2 ½, or 3 In∣ches, and the Diameter of whose Cavity as well at the upper as lower Orifice (should have been just 3. Inches, but through the errour of the workman) was 3. inches and 2/10. To this Hoop we successively fasten'd with Cement divers round pieces of Glass, such as is used by Glasiers (to whose Shops we sent for it) to make Panes for Windows, and thereby made the Brass-ring with its

Glass-cover a kind of Receiver, whose open Orifice we carefully cemented on to the Engine; and then we found, as we had conje∣ctured, that usually at the first Exuction (though sometimes not till the second) the Glass-plate would be broken inwards with such violence, as to be shatter'd into a great multitude of small fragments, and (which was remarkable) the irruption of the ex∣ternal Air driving the Glass inwards did constantly make a loud Clap, almost like the Report of a Pistol. Which Phaenomenon, whether it may help us to discover the cause of that great noise, that is made upon the discharging of Guns, (for the Recoyl seems to depend upon the Dilatation and Impulse of the Powder,) I must not stay to consider.