Physiologia Epicuro-Gassendo-Charltoniana, or, A fabrick of science natural, upon the hypothesis of atoms founded by Epicurus repaired [by] Petrus Gassendus ; augmented [by] Walter Charleton ...

SECT. VI. The Fifth Capital Difficulty.

WHat Force that is, whereby the Aer,* 1.1 admitted into the lower ori∣fice of the Tube, at the total eduction thereof out of the restagnant Quicksilver and Water; is impelled so violently, as sufficeth not only to the ele∣vation of the remaining Liquors in the Tube, but even to the discharge of them through the sealed extreme, to a considerable height in the Aer?

Solution.

The immediate Cause of this impetuous motion,* 1.2 appears to be only the Reflux, or Resilition of the so much compressed Basis of the Cylindre of Aer, impendent on the surface of the Restagnant Liquors, Quicksilver and Water, to the natural Laxity of its insensible particles upon the cessation of the force Compressive: the Principle, and manner of which Restorative or Re••lexive Motion, may be perspicuously deprehended, upon a serious re∣cognition of the Contents of the last Article in the praecedent Chapter of a Disseminate Vacuum; and most accommodately Exemplified in the dis∣charge or explosion of a bullet from a Wind-Gun. For, as the insensible particles of the Aer included in the Tube of a Wind-Gun, being, by the Embolus or Rammer, from a more lax and rare contexture, or order, re∣duced to a more dense and close (which is effected, when they are made more contiguous in the points of their superfice, and so compelled to di∣minish

the inane spaces interjacent betwixt them, by subingression) are, in a manner so many Springs or Elaters, each whereof, so soon as the external Force, that compressed them, ceaseth (which is at the remove of the Diaphragme or Partition plate in the chamber of the Tube) re∣flecteth, or is at least reflected by the impulse of another contiguous parti∣cle: therefore is it, that while they are all at one and the same instant executing that Restorative Motion, they impel the Bullet, gaged in the canale of the Tube, before them with so much violence, as enables it to transfix a plank of two or three digits thickness. So also do the insensi∣ble Particles of the Base of the Cylindre of Aer incumbent on the surface of the Restagnant Liquors, remain exceedingly compressed by them, as so many Springs bent by external Force: and so soon as that Force ceas∣eth (the Quicksilver in the Tube, after its eduction, no longer pressing the Restagnant Mass of Quicksilver underneath, and so that by his tumefaction no longer pressing the impendent Aer) they with united forces reflect themselves into their natural rare and liberal contexture, and in that Resto∣rative motion drive up the remainder of Quicksilver in the canale of the Tube to the upper extreme thereof with such violence, as sufficeth to ex∣plode all impediments, and shiver the glass.

* 1.3For, in this case, we are to conceive the Aer to be aequally distressed betwixt two opposite Forces; on one side by the Gravity of the long Cy∣lindre of Aer from the summity of the Atmosphere down to the Base im∣pendent on the superfice of the Restagnant Liquors; on the other, by the ascendent Liquors in the subjacent vessel, which are impelled by the Cy∣lindre of Quicksilver in the tube, descending by reason of its Gravity: and consequently, that so soon as the obex, Barricade, or impediment of the Restagnant Quicksilver, is removed, the distressed Aer instantly con∣verteth that resistent force, which is inferior to the Gravity of the incum∣bent aereal Cylindre, upon the remainder of the Quicksilver in the Tube, as the now more superable Opponent of the two; and so countervailing its Gravity by the motion of Reflexion or Restoration, hoyseth it up with so rapid a violence,* 1.4 as the easily frangible body of the Glass cannot sustain.

Which Reason doth also satisfie another Collateral Scruple, viz. Why Water, superaffused upon the Restagnant Quicksilver, doth intrude it self as it were creeping up the side of the Tube, and replenish the Desert Space therein; so soon as the inferior orifice of the Tube is educed out of the Re∣stagnant Quicksilver, into the region of Water. For, it is impelled by the Base of the Aereal Cylindre exceedingly compressed, and relaxing it self: the resistence of it, which was not potent enough to praevail upon the greater Gravity of the Quicksilver in the Tube, so as to impel it above the point of Aequiponderancy; being yet potent enough to elevate the Water,* 1.5 as that whose Gravity is by 13 parts of 14 less then that of the Quicksilver.

Here the Inquisitive may bid us stand, and observe a second subordi∣nate Doubt, so considerable, as the omission of it together with a rational solution, must have rendred this whole Discourse not only imperfect, but a more absolute Vacuum, i. e. containing less of matter, then the Desert Space in the Tube; and that is: How it comes, that during the Aequi∣librium

betwixt the ••eight of the Quicksilver in the Tube on the one hand, and the long Cy••lindre of Aer on the other, even then when the Base of the Cylindre of Aer is compressed to the term of subingression; we find the aer as Fluxile, soft, and yeilding, (for, if you move your hand trans∣versly over the Restagnant Quicksilver, you can deprehend none the least Tensity, Rigidity, or Urgency thereabout) as any other part of the Region of Aer not altered from the Laxity of its natural con∣texture?

We reply,* 1.6 that though nothing occurr in the whole Experiment more worthy our absolution; yet nothing occurrs less worthy our admiration then this. For, if my hand, when moved toward the region of the compressed Aer, did leave the space, which it posses∣sed before motion, absolutely Empty, so as the aer impelled and dis∣lodged by it could not circulate into the same; in that case, indeed, might I perceive, by a resistence obvening a manifest Tensity or Ri∣gidity in the compressed aer: but, insomuch as when my hand leaves the region of the lax aer, and enters that of the compressed, there is as much of space lest in the lax aer for the compressed to re∣curr into, as that which my hand possesseth in the region of the compressed; and when it hath passed through the region of the compress'd, and again enters the confines of the lax, there is just so much of the lax aer propelled into the space left in the compres∣sed, as responds in proportion to the space possessed by it in the lax: therefore doth my hand deprehend no sensible difference of Fluxility in either, and yet is the Urgency or Contention of the Base of the Cy∣lindre of aer impendent upon the restagnant Quicksilver, constantly e∣qual, though it may be conceived to suffer an Undulation or Wavering motion by the traversing of my hand to and again, by reason of the pro∣pulse and repulse.

This may be enforced by the Example of the Flame of a Can∣dle;* 1.7 which though ascending constantly with extreme pernicity, or ra∣pidity of motion, and made more crass and tense by the admixture of its own ••uliginous Exhalations: doth yet admit the traversing of your finger to and fro through it so easily, as you can deprehend no diffe∣rence of Fluxility between the parts of the Flame and those of the cir∣cumvironing Aer; the cause whereof must be identical with the for∣mer.

Secondly, by the Experience of Urinators or Divers;* 1.8 who find the Ex∣tension and contraction of their arms and legs as free and easie at the depth of 20 fathoms▪ as within a foot of the surface of the Water; not∣withstanding that water comes many degrees short of Aer, in the point of * 1.9 Fluidity.

* 1.10Thirdly, by the Beams of the Sun; For, when these insinuate themselves through some slender hole or crany into a chamber, their stream or Thread of Solary Atoms appears like a white shining wand (by reason of those small Dusty bodies, whose many faces, or superficies making innumerable re∣fractions and reflections of the rayes of Light towards the Eye) and con∣stantly maintains that figure, though the wind blow strongly transverse, and carry off those small dusty bodies, or though with a fan you totally dispel them: why? Because fresh Particles of Dust succeeding into the rooms of those dispelled, and aequally refracting and reflecting the incident radii of light toward the Eye, conserve the Apparence still the same. So though the wind blow off the first Cylindre of comprest aer, yet doth a se∣cond, a third, &c. instantly succeed into the same Space, so as that region, wherein the Base thereof is situated, doth constantly remain comprest: be∣cause the compression of the insensible Particles of the Aer and Wind, du∣ring their Continuation in that region, continues as great as was that of the particles formerly propulsed and abduced.

* 1.11And Fourthly, by the Rainbow; which persisteth the same both in the extent of its Arch, and the orderly-confused variety of Colours: though the Sun, rapt on in his diurnal tract, shifts the angle of incidence from one part of the confronting Cloud to another, every moment; and the Wind change the Scene of the Aer, and adduce consimilar small bodies, whose various superficies making the like manifold Refractions and Reflexions of the incident lines of Light, dispose them into the same colours, and prae∣sent the eye with the same delightful Apparition.

* 1.12Which had the Hairbrain'd and Contentious Helmont in the least mea∣sure understood; he must have blush't at his own most ridiculous whimsy, that the Rainbow, is a supernatural Meteor, or Ens extempore created by Di∣vinity, as a sensible symbol of his Promise no more to destroy the inhabi∣tants of the Earth by Water, having no dependence at all on Natural Cau∣ses: especially when the strongest Argument He could excogitate, whereby to impugn the common Theory of the Schools, concerning the producti∣on thereof, by the refraction and reflection of the rayes of the Sun incident upon the variously figured parts of a thin and rorid Cloud in opposition diametrical; was only this. Oculis, manibus, & pedidus cognovi istius fig∣menti falsitatem. Cùm ne quidem simplex Nubes esset in loco Iridis. Neque enim, etsi manu Iridem finderem, eamque per colores Iridis ducerem, sensi quid∣piam, quod non ubique circumquaque in aere vicino: imo non proin Colores ••ridis turbabantur, aut confufionem tollerabant. (in Meteor on Anomalon.)

Notes

• * 1.1

  Art. 1. The Fifth Principal Dif∣ficulty.
• * 1.2

  Art. 2. Solved, by the Motion of Re∣stauration na••u∣ral to each in∣sensible parti∣cle of Aer.
• * 1.3

  Art. 3. The incum∣bent Aer, in this case, e∣qually distres∣sed, by two contrary For∣ces.
• * 1.4

  Art. 4. The motion of Restaurati••n in the Aer, ex∣tended to the satisfaction of another consi∣milar Doubt, concerning the subintrusi∣on of VVater into the Tube; if superaffused upon the re∣stagnant Mer∣cury.
• * 1.5

  Art. 5. A Third most important Doubt, concer∣ning the non∣apparence of any Tensity, or Rigidity in the region of Aer incum∣bent upon the Restagnant Liquors.
• * 1.6

  Art. 6. The solati••n thereof, by the necessary re∣liction of a space in the 〈◊〉〈◊〉 regi••n of Lax aer, e∣qual to that, which the Hand commo∣ved possesseth in the region of the Com∣prest.
• * 1.7

  Art. 7. A confi••ma••i∣on of the same Reason, by the adaequate Ex∣ample of the Flame of a Ta∣pour.
• * 1.8

  Art. 8. 2 By the Ex∣periment of Vrination.
• * 1.9

  Quam ob caussam, corpus h••m••nus ad 〈…〉〈…〉 nullum incumbentis aquae p••ndus sentiat, lector 〈…〉〈…〉 Hyd••aul••••. 〈…〉〈…〉 p. ••05.
• * 1.10

  Art. 9. 3 By the Beams of the Sun, entring a room, through some slender crany, in the appearance of a white shining VVand, and constantly maintaining that Figure, notwithstand∣ing the agita∣tion of the aer, by wind, &c.
• * 1.11

  Art. 10. 4 By the con∣stancy of the Rainbow, to its Figure, not∣withstanding the change of position and place of the cloud & con∣tiguous aer.
• * 1.12

  Art. 11. Helmonts Dell∣rium, that the Rainbow is a supernatural Meteor; obser∣ved.