The works of the Honourable Robert Boyle, Esq., epitomiz'd by Richard Boulton ... ; illustrated with copper plates.

EXPERIMENT I. Concerning the Raising of Mercury a great Height in an open Tube, by the Spring of a small Quan∣tity of included Air.

IN order to make an Estimate of the Force of the Air's Spring, in it's several Degrees of Expansion; We fill'd the fourth part of a Viol with Quicksilver, the Neck of which was none of the largest, in which we fix'd a Glass Tube with hard Wax, the lower End reaching almost to the Bottom of the Quicksilver, and the up∣per almost a Yard above the Viol, which being conveigh'd into a Receiver (See Plate 5. Fif. 1.) which was pretty Tall,* 1.1 upon an Exsuction of the Air in the Receiver, that in the Viol ex∣panding

it self, rais'd the Mercury 27 Inches in the Tube; yet when the Air was again admitted into the Receiver, it subsided so far as to be al∣most; if not quite equal with the Surface of the Mercury in the Viol: And this Experiment was try'd before the Famous Savilian Geometer Dr. Wallis, tho' it does not constantly succeed alike, it sometimes rising higher than at others.

In which Experiment the following Observa∣tions were to be made. First, That so much Air being blown into the Viol, to try whether it was stanch, as was able to raise the Mercury three Inches in the Pipe, upon the Exsuction of the External Air in the Receiver, the Mercury rose 30 Inches above that in the Viol.

Secondly, When the Mercury is taken out of the Receiver, it does not suddenly subside as low as before it's Ascent, the Air being a little more Expanded by the Heat of the Cement when melted with an Iron.

Thirdly, Whilst the Air included in the Viol retains any considerable Springiness, after each Exsuction the Mercury will be rais'd by the Force of its Expansion, a considerable Height above what that Air is able to suspend it at, and makes several Vibrations before it settles.

Fourthly, Upon the first Exsuction the Mercu∣ry rises near ⅔ of the whole Weight that the Expansion of the included Air is able to raise it, and continues every subsequent Exsuction to rise less and less as the weight of the suspended Mer∣cury encreases, and the Spring of the Internal Air grows weaker, and as the Mercury rises less every Exsuction than it did before, so are the Vibrations less considerable.

Lastly, Having observ'd the Weight of the Air in a good Barometer, when it was but light, the Mercury was rais'd to 29 and ⅜ tho' soon af∣ter the Tryal it was but 29 Inches high.

To make an Estimate of the Quantity of Air which rais'd the Mercury to the usual height, we counterpois'd the Viol, and then filling it full of Water, we found it to weigh about 5 Ounces 2 Drachms, and about 20 Grains; but so much being pour'd off, that the remaining Water on∣ly filled the Space which the Mercury was before contain'd in, it weigh'd 1 Ounce 2 Drachms 14 Grains, so that the Air which by it's Expansion elevated the Mercury, fill'd the Space of no more than 4 Ounces and a few Grains: The Diameter of the Pipe employ'd in this Experiment was no more than the ⅛ of an Inch.

* 1.2But besides the Spring of the Air, from this Experiment we may learn, what is to be thought of what some Learned Men teach concerning the Suspension of Quicksilver by a Funiculus, and, it's rising to avoid a Vacuum; for were the first true, it might be demanded, why that Funicu∣lus raises it not above 27 Inches; and as for the latter it's objected, that the Mercury being unable adequately to fill up more Space by rising, than if it rose not, the Reason must be invalid.

Notes

• * 1.1

  See Plate 5. Fig. 1.
• * 1.2

  An Argu∣ment a∣gainst a Fuga vacui.