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

EXPERIMENT II. An Attempt to discover the Motion of Aether in the Exhausted Receiver.

HAving instead of the Glass Tube mention'd in the former Experiment, provided a crooked one of Brass,* 1.1 such as the first Figure represents, and joyn'd a Glass Tube to the short∣er Leg with Cement, we caus'd Weights to be fixed to the Top of the Sucker to depress it speedily when occasion required: This Syringe was fixed to a Pedestal to keep it firm, and to hinder it from tottering; and a Feather was likewise fixed with Cement to the lower End of the Syringe, so that the small End was placed above the Orifice of the crooked Tube. All which being conveyed into a Receiver, and the Pump set on Work, we observ'd, that, the Suck∣er by the help of the Turning-Key being of∣ten elevated and permitted to fall again, the Feather was gradually less shaken, with what was forced out of the Syringe, as the Receiver was more and more exhausted, till at the last the Feather did not seem in the least to be mo∣ved, before Air was again let in, and then it was blown up as before: In which Experiment we observ'd, that as the Cavity of the Receiver was more or less exhausted, the Descent of the Sucker was accordingly quickened, so that had there been a Substance finer than Air in the Re∣ceiver, the Blast would have been greater as the Descent of the Sucker was swifter.

We tryed the same Experiment a second time, contriving to draw up the Sucker higher than we did before, but the Event was no more sa∣tisfactory than the former.

But that I might be informed, what Quan∣tity of Air was drawn out every Exsuction, as well as when the Feather was more or less sha∣ken by the Wind thrown out of the Syringe, I made use of a Glass Tube, such as Figure the Third represents,* 1.2 instead of the former Brazen One; and the one End being immersed in a Jar, and placed in the Receiver, as the Air was pum∣ped out, several Bubbles broke through the Wa∣ter out of the Pipe, but External Air getting in at a Leak, the Water was pressed up into the Pipe again; nevertheless, upon an Exsuction of that Air it again subsided; yet yielded so ma∣ny Bubbles, that we could not conveniently make any further Observations, till the Recei∣ver having stood still for some time, the Water was freed from Air; and then, tho' the Pump was set on Work, till the Gage discovered the Receiver to be very well exhausted; yet we could not discern, that any Bubbles were forced through the Water in the Bottom of the Tube by fre∣quently elevating and depressing the Sucker; for tho' there appear'd a few in the Top of the Water, yet we judged that those rather pro∣ceeded from some aery Particles lodging in the Pores of the Water.

But what was most Remarkable in this Expe∣riment was, that after some time the Water ri∣sing about an Inch in the Tube, above the Sur∣face of the Water without it, we several times rais'd the Sucker 2 or 3 Inches, and fuffered it

to fall again, without perceiving, that the Wa∣ter in the Tube was in the least Affected; which is an Argument either of a Vacuum, or that the Parts of that Aether are so fine, that they exceed the Rarefaction of the Air so far, as not to be able to effect what a Particle of Air does which is not above 1/500 part of the Quan∣tity of a Pin's head; a Particle of Air, before Expansion, of that Minuteness being able, when the Receiver is exhausted, to displace much more Water upon their Expansion than this Ae∣ther.

By which Experiment, as well as what we have taken notice of, the Reason I formerly as∣sign'd for the rising of Water in Syphons seems to be confirm'd; the Water in the Pipe made use of in these Experiments, not being able to rise when the Air was exhausted, tho' the Suck∣er was drawn up, till Air was permitted to en∣ter into the Receiver again.

Notes

• * 1.1

  See Plate 1. Fig. 1.
• * 1.2

  See Plate 1. Fig. 3.