CHAP. VII.

Concerning the Space derelicted by the de∣scent of the Mercury in the Torricellian Experiment, and what it is not, or what it is that fills it.

HAving gone through the two pre∣mised Considerations, prelimi∣nary to this Inquiry, I now come to the third General, namely what it is that fills the space derelicted by the descen∣ding Mercury in the Tube. And first I shall consider, whether it be a Space purely void of any Body. 2. If it hath some Body that fills that Space, I shall consider what it is not that fills it. 3. I shall consider what it is that most pro∣bably may be thought to fill it.

First therefore I say it is not Nothing, or a pure Vacuity, but it is some cor∣poreal substance that succeeds in the head of the Tube, derelicted by the Mer∣cury.

And here 1. I shall not enter into Page  118any large debate touching the possibili∣ty or impossibility of interspersed or coacervated vacuities in any parts of the Universe; neither 2. shall I insist upon those obscure evidences of the in∣existence of a Body in that derelicted space; as namely the communication of Sounds, or the reception of Light, or transmission of Colours, or other vi∣sible species in or from it. But 3. I shall ground my Conclusion from those more sensible and apparent Phaenomena which do evince it; namely, those sensible plain Effects in that seeming empty Space, which could never be produeed but by the contiguity and presence of some corporeal substance, filling that supposed empty space.

1. It is most evident to any man's sense that will but try it, that if the Tube be open at both ends, and filled up with Mercury, and then one end stopped with the finger, and the other end inverted and immersed in the restagnant Mer∣cury, whereby it descends from the top of the Tube, a strong and sensible At∣traction is wrought upon the pulp of Page  119the upper finger that closeth it, which continues and grows more and more forcible, sensible, and evident, the farther the Mercury is removed from the upper end, and approaching to its usual station of 29 Inches.

This Attraction is impossible to be without the contiguity of some Body to the pulp of the finger, which cannot be the Mercury it self, for That in a Tube of four Foot long is removed a∣bove a Foot distant from the finger, by that time it comes to its station; yet all this while the strong suction upon the pulp of the finger continues.

And they that go about to tell us, that it is not Attraction or Suction by any power within the Tube, but by the pulsion of the incumbent column of Air, need no other confutation than their own sense to assure them the con∣trary; for most evidently the force that the finger feels is from within, and not from without: and this Solution by Pulsion, is given only to gratifie that imaginary Supposition that some have entertained of the Aery Column, where∣of in due time.

2. The instance of Hanoratus Fabri in the 6^th of his Physical Dialogue, (though not tryed by myself, yet asserted to be tryed by him) puts it out of question. If at the upper end of the Tube there be fixed a folded Paper, which may be extended by any force, but otherwise contracting it self (in the manner of Paper-Lanthorns made by School-boys), this plicat a charta will by the subsiding of the Mercury be unfolded and exten∣ded, which could not be, but by the contiguity of some Body unto it.

3. The instance given by Linus, and improved by Fabri, ubi supra, of an emp∣ty Bladder close tyed, and fastned to the upper end and the inside of the Tube, extended after the descent of the Mer∣cury, and again contracting it self to its former dimension by the inclination of the Tube, makes it plain, that this Extention is the effect of some included Body in that relicted space, which is not the bare gross body of the Mercury, which is removed a Foot or more below it, and in which there is not so much as pretended to be any Magnetick qua∣lity Page  121in relation to the Bladder.

And they that tell us it is the Elatery of the Air included in the Bladder, that extends it by a natural expansion, tell us an invention fitted to serve the Suppo∣sition of the prodigious natural Elatery of uncompress'd Air, whereof hereaf∣ter.

It is true, that if this Bladder hath any little orifice, or hole open in it, the distention will not ensue; but the rea∣son thereof is evident, (not upon their Supposition of the impediment of the natural Elater of the Air included in the Bladder,) but because in that case the Attraction is made as well upon the inside of the Bladder through the orifice, as upon the outside, and so the Bladder obtains the same consistence as at first; but where there is no orifice, the Attraction can only be but upon the outside of the Bladder, upon which there necessarily follows an Extension of the Bladder, and a necessary Conse∣quent thereof is a Dilatation and Ex∣pansion of that little particle of Air in∣cluded in it, to the uttermost dilatation Page  122that that attractive force can give it, or produce in it, which is not by natural Elasticity, but by forcible Tension.

Upon these and the like sensible and plain Instances it seems undeniable by any, that will not abandon his own sense, that it is not Nothing that is in that derelicted space, but it is some bo∣dily substance; for otherwise it were impossible that those, and the like sensible effects could be produced: for regular∣ly, all natural bodily effects are wrought by a contact of some Active body up∣on the Patient.