A defence of the doctrine touching the spring and weight of the air propos'd by Mr. R. Boyle in his new physico-mechanical experiments, against the objections of Franciscus Linus ; wherewith the objector's funicular hypothesis is also examin'd, by the author of those experiments.

CHAP. VI.

HIs fourth Chapter, wherein the Title promises that he will prove, Argentum in loco occluso non sustentari à lapsu per ip∣sum aëris Elaterium, is very short, and does not require that we should dwell long upon it. For the proof he brings of his Asser∣tion being this, Cum tota vis hujus Elaterii pendeat à re∣futato jam aëris aequipondio cum digitis 29½ Argenti vivi, * 1.1 ita ut nec plus net minus faciat hoe elaterium in loco occluso quam fit-per illud aequipondium in loco aperto; manifestum est, cum jam oftensum sit fictitium planè esse hujusmodi aequipondium, fictitium quo{que} esse tale elaterium: This being no new Argument, but an Inference from those he had set down in the former Chapter, by our Answers to them it is become needless for us to make any di∣stinct Reply to this. We shal rather desire the Reader to take no∣tice, that whereas our Author sayes that according to his Adver∣saries, Ncc plus nec minus faciat hoc Elaterium in loco occluso quam fit per illud Aequipondium in loco aperto; whatever others may have written, we for our part allow of this Opinion but in some Cases; for in others we have perform'd much more by the Spring of

the Air, which we can within certain limits increase at pleasure, then can be perform'd by the bare weight, which for ought we know remains alwayes somewhat near the same. And of this advantage that the Spring of the Air may have in point of force above the weight of it, we have formerly given an Instance in our 17. Experiment, (where, by compressing the Air in the Receiver, we impell'd the Mercurial Cylinder higher then the station at which the Counterpoise of the Air is wont to sustain it) and shall hereafter have occasion to give yet more conside∣rable proofs. To the lately recited words our Examiner sub∣joyns these; Adde, cum allata jam capite praecedente ex∣perimenta de adhaesione digiti, &c. eodem modo se habent in * 1.2 loco clauso ac in aperto, necessarium esse facta ex eis argumenta contra aquipondium, eadem quo{que} contra elaterium vim habere. But though he propose this as a new Argument, yet since 'tis built but upon the adhesion of the Finger (of which we have already given an account in our Hypothesis) I see not how it requires any new and particular Answer. And whereas he sayes, that the Experiments he had mentioned concerning the adhesion of ones Finger, &c. eodem modo se habent in loco clauso ac in aperto; I could wish he had added what way he took to make the Tryals. For he gives no intimation that he did them any other wayes then in ordinary rooms. And in such there scarce ever wants a communication betwixt the inward and outward Air, either at the Chimney, or Window, or Door not exactly shut, or at some hole or crevice or other, by means of which the weight of the Atmosphere has its operation within the room.

To his second Argument our Author adds not a third, unless we take that for an Argument which he immediately annexes to his last recited words: Et profectò (sayes he) si secum ex∣penderent hi Authores, quanta sit difficultas explicandi hu∣jusmodi * 1.3 aëris elaterium, nisi idem aër se solo occupet majorem locum (ut paulo ante) credo eos sententiam facilè mutaturos. But this being said gratis, does not exact an Answer; and he must make it more intelligible then any man that I know of has yet done,

how the same Air can adequately fill more space at one time then at another, before he perswade me to change my opini∣on about the Spring of the Air: Especially since he himself allowes that the Air has a Spring, whereby it * 1.4 is able, when it has been violently compress'd, to recover its due extension; the manner whereof if he will intelligibly explicate, his Adversaries will have no great difficulty to make out the Spring of the Air. But whether his Hypothesis, or ours, be the more intelligible, will be more properly considered in the second part of our Discourse, to which we will therefore now proceed.

Notes

• * 1.1

  Pag. 20.
• * 1.2

  Pag. 21.
• * 1.3

  Pag. 21.
• * 1.4

  Pag. 11.