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 ...

Solution.

* 1.1The Resistence of the parts of the aer, which endures no compression, or subingress of its insensible particles, beyond that certain proportion, or de∣terminate rate.* 1.2

To profound this mystery of Nature to the bottom, we are to request our Reader to endure the short recognition of some passages in our prae∣cedent discourses. (1) That upon the ordinary translation of bodies through the Aer, the resistence of its insensible parts is so small, as not to be discoverable by the sense; because the subingression of its contiguous parts into the loculaments of the next vicine aer, is only perexile, or su∣perficial: and that we may safely imagine this superficial subingression not to be extended beyond the thickness of a single hair; nay, in some

cases, perhaps, not to the hundreth part thereof. So stupendiously subtle are the fingers of Nature in many of her operations. But, that the resistence observed in the present Experiment, for the enforcing of a praeternatural Vacuum, is therefore deprehensible by the sense, because in respect of a defect of place behind the body propellent, into which the parts of the aer compelled forward may circulate, the subingression must be more pro∣found; and so the resistence being propagated farther and farther by de∣grees, must grow multiplied, and consequently sensible. (2) That the Force of the body propellent is greater, then the force of the next conti∣guous aer protruding the next, and the force of the third protruded wave of the aer (for a kind of Undulation may be ascribed to aer) greater on the Fourth, then that of the Fourth upon the Fifth, and so progressionally to the extrem of its diffusion or extension: so that the Force becomes so much the weaker and more oppugnable, by how much the farther it is ex∣tended; and dwindles or languishes by degrees into a total cessation. (3) That, as upon the succussion, or shock of a Bushel apparently full of Corn, is left a certain sensible space above, unpossessed by any part or Grain thereof; which coacervate empty space responds in proportion to those many Disseminate Vacuola, or Loculaments intercepted among the incontingent sides of the Grains, before their reduction to a more close or∣der by the succussion of the Bushel: so likewise, upon the impulse of the aer by a convenient body, is left behind a sensible space absolutely empty, as to any part of aer; which Coacervate empty space must respond in proportion to those many Disseminate spaces intercepted among the in∣contiguous parts, or Granules of the aer, before their reduction to a more close order, or mutual subingression and coaptation of sides and points, by the body compressing.

These Notions recogitated,* 1.3 our speculations may progress with more advantage to explore the proxime and proper Cause of the Mercuries con∣stant subsistence at the altitude of 27 digits, in the Tube perpendicularly erected. For, upon the credit of their importance, we may justly assume; that upon the compression of the circumambient Aer by a small quantity of Quicksilver (suppose only of two or three inches) impendent in the con∣cave of the tube, can be caused, indeed, some small subingression of the particles thereof; but such, as is only superficial and insensible: in respect the weight of so small a proportion of Quicksilver is not of force sufficient to propel the parts of the aer to so great a crassitude that the space de∣tracted from the Aggregate of Disseminate Vacuities should amount to that largness, as to become visible above the Quicksilver in the Tube; since the quantity of the Quicksilver being supposed little, the force of Reluctan∣cy, or Resistence in the parts of the aer, arising from their inhaerent Fluidi∣ty, must be greater then the force of compression arising from Gravity; and therefore there succeeds no sensible Deflux of the Quicksilver. But, being that a greater and greater mass of Quicksilver may be successively infused into the Tube, and so the compressive force of its Gravity be re∣spectively augmented; and thereupon the aer become less and less able suc∣cessively to make resistence: 'tis difficult not to observe, that the pro∣portion of Compression from Gravity in the Quicksilver, may be so equa∣lized to the Resistence from Gravity in the Aer, as that both may remain in statu quo, without any sensible yeilding on either side. Hence comes it, that at the aequipondium of these two Antagonists, the space in the

Tube detracted from the Aggregate of minute Inanities disseminate in the aer, is so small as not to be commensurated by sense: and at the cessation of the Aequilibrium, or succeding superiority of the encreased weight of the Quicksilver, the parts of the Aer being compelled thereby to a farther retrocession and subingression; the space detracted from the Aggre∣gate of disseminate Vacuities in the aer, becomes larger, and conse∣quently sensible, above the Quicksilver in the upper region of the Tube.

* 1.4This may be most adaequately illustrated, by the simile of a strong man, standing on a plane pedestal, in a very high wind. For, as He by a small afflation or gust of wind, is in some degree urged or prest upon, though not so much as to cause him to give back; because the force of his resi∣stence is yet superior to that of the Wind assaulting and impelling him; nor, when the force of the Wind grows upon him even to an Aequilibrium, is He driven from his station, because his resistence is yet equal to the im∣pulse of the wind; but when the force of the Wind advances to that height, as to transcend the Aequilibrium, then must the man be compelled above the rate of his resistence, and so be abduced from the place of his station: so likewise, while there is only a small quantity of Quicksilver contained in the Tube, though, by the intervention or mediation of the Quicksilver restagnant in the subjacent vessel, it press upon the parts of the incumbent aer, in some degree; yet is not the aer thereby urged so, as to be compel∣led to retrocede, and permit the restagnant Quicksilver to ascend higher in the vessel; and therefore the Quicksilver impendent in the Tube cannot descend, because the restagnant wants room to ascend. But, when the quantity, and so the Gravity of the Quicksilver contained in the Tube is so augmented, as to exceed the Resistence of the aer; then is the aer com∣pelled or driven back, by the restagnant Quicksilver rising upwards, to a sensible subingression of its atomical particles, and the Quicksilver in the Tube instantly defluxeth into the place resigned by the restagnant, until it arriveth at that point of altitude, or standard, where the resistence of the aer becomes again equal to the force compressing it, and there subsisteth, after various reciprocations up and down in the Tube.* 1.5

Now concerning the remaining, and, indeed, the most knotty part of the Difficulty, viz. Why the Aequilibrium of these two opposite Forces, is constant to the certain praecise altitude of 27 digits? of this admirable Mag∣nale no other cause seems worthily assignable, but this; that such is the na∣ture of aer, in respect both of the atomical particles of which it is composed, and of the disseminate vacuities variously interspersed among them, as that it doth resist compression at such a determinate rate, or definite proportion, as ex∣actly responds to the altitude of 27 digits. Should it be demanded of us, Why He,* 1.6 who stands on a plane, doth resist the impulse of a mighty wind to such a determinate rate or height, but not farther: we conceive our An∣swer would be satisfactory to the ingenious, if we returned only, that such is the exact proportion of his strength, resulting from the individual tem∣perament of his body.

We are Men, i. e. Moles; whose weak and narrow Opticks are ac∣commodated only to the inspection of the exterior and low parts of Nature, not perspicacious enough to penetrate and transfix her interior and abstruse Excellencies: nor can we speculate her glorious beauties in the direct and

incident line of Essences and Formal Causes, but in the refracted and reflected one of Effects; nor that, without so much of obscurity, as leaves a mani∣fest incertitude in our Apprehensions, and restrains our ambition of inti∣mate and apodictical Science, to the humble and darksome region of mere superficial Conjecture. Such being the condition of our imperfect Intel∣lectuals; when we cannot explore the profound recesses, and call forth the Formal Proprieties of some Natures, but find our disquisitive Faculties ter∣minated in the some Apparences, or Effects of them: it can be no deroga∣tion to the dignity of Humanity, for us to rest contented, nay thankful to the Bounty of our Creator, that we are able to erect verisimilous Conje∣ctures concerning their causation, and to establish such rational Appre∣hensions or Notions thereupon, as may, without any incongruity, be laudably accommodated to the probable solution of other consimilar Effects, when we are required to yeild an account of the manner of their arise from their proper originals. Thus, from our observation of other things of the like condition, having extracted a rational Conjecture, that this so great Gravity of the Quicksilver doth depend upon the very Con∣texture of its insensible particles, or minute bodies, whereof it doth con∣sist, by which they are so closely and contiguously accommodated each to other in the superficies of their points and sides, as no body whatever (Gold only excepted) doth contain more parts in so small a bulk, nor con∣sequently more Ansulae, or Fastnings, whereon the Magnetique Hooks of the Earth are fixable, in order to its attraction downward: and on the contrary, that the so little Gravity of the Aer, depends on a quite dissi∣milar Contexture of its insensible particles, of which it is composed, by which they are far less closely and contiguously adapted each to other, and so incomparably fewer of them are contained in the like space, and consequently have incomparably fewer Ansulae or Fastnings, whereon the Hooks of the Magnetick Chains of the Earth may be fixed: having, we said, made this probable conjecture, what can be required more at our hands, then to arrest Curiosity with this solution; that the Aer is of such a Nature, i. e. consisteth of such insensible particles, and such Inane Spaces interspersed among them, as that it is an essential propriety of it, to resist compression, to such a determinate rate, and not beyond? Had we bin born such Lyncei, as to have had a clear and perspect Knowledge of the Atoms of Aer, of their Figure, magnitude, the dimensions of the Inane spaces intercepted among them, of the facility or difficulty of their reciprocal adaptation, of the measure of their Attraction, the manner and velocity of their Tendency, &c. then, indeed, might we, without any complex cir∣cumambage of Discourse, have rendered the express and proper Reason, why the Aer doth yeild praecisely so much, and no more to the Gra∣vity of the Quicksilver compressing it. Since we were not, it may be reputed both honour and satisfaction, to say; that it is essential to the Na∣tures of Mercury and Aer, thus and thus opposed, to produce such and only such an Effect.* 1.7

However, that we may not dismiss our Reader absolutely jejune, who came hither with so great an Appetite; we observe to him, that the con∣stant subsistence of the Mercury at the altitude of 27 digits, doth seem ra∣ther to proceed from the manifest Resistence of the Aer, then from any se∣cret Quality in the Mercury, unless its proportion of Gravity be so con∣ceived. This may be collected from hence; that Water infused into the

Tube doth also descend to the point of Aequipondium, and stops at the al∣titude of 32 Feet, nor more, nor less; and in that altitude becomes aequi∣ponderant to the Mercury of 27 digits. So that it is manifest, that with what Liquor soever the Tube be filled, still will the Aer resist its deflux at a certain measure: provided only, that the Tube be long enough to receive so much of it, as the weight thereof may equal that of the Mercury at 27 digits, or the Water at 32 feet.

* 1.8Here we meet an opportunity also of observing to Him, by how admi∣rable an Analogy this respective Aequality of the weights of Quicksilver and Water, in these so different altitudes, doth consent with the absolute weight of each. When, as the weight of Quicksilver carries the same proportion to the weight of Water, of the same measure or quantity, as 14 to 1: so reciprocally doth the Altitude of 32 feet, carry the same pro∣portion to 27 digits, as 14 to 1. And hence comes it, that, if Water be s••peraffused upon the restagnant Quicksilver in the vessel under the Tube; the Quicksilver doth instantly ascend above the standard of 27 digits, higher by a 14^••. part of the water superaffused. Which truly, is no im∣manifest argument, that the Aer, according to the measure of its weight, or the praecise rate of its resistence, becomes aequilibrated to the Mercury at the altitude of 27 dig. since the superaffused Water doth no more then advance the Aequilibrium according to the rate of its weight, or propor∣tion of resistence. Besides, it is farther observable, that because the Tube is replenished by a 14^th part in 27 dig. of the altitude, above the first Ae∣quilibrium (a proportionate access to the Mercury in the Tube, being made by a like part of that in the subject vessel, impelled into it) therefore is the Vacuum above the Mercury in the Tube, diminished also by one 14^th. part; and the compression of the Aer, impendent on the surface of the restagnant Mercury, relaxed and diminished also by a 14^th part. So that if the vessel underneath the Tube be large enough to admit an addition of Water suc∣cessively affused, until so much of the restagnant Mercury, as formerly de∣scended, shall be again propelled up into the Tube: then must the whole Tube be replenished, and so the whole Vacuity disappear, for then all Compression of the incumbent aer ceaseth, and so much space as was possessed before the Experiment, both without and within the Tube, by the Mercury, Water, Aer, is again repleted.

* 1.9If you shall still insist, and urge us to a praecise and definite account of the weight of the Quicksilver contained in the Tube to the altitude of 27 digits, and of the Water of 32 feet; which makes the Aequilibrium with the opposite weight of the circumstant Aer: our Answer is, that the exact weight of neither can be determined, unless the just Diameter or Ampli∣tude of the Tube be first agreed upon. For albeit neither the Longitude nor the Amplitude of the Tube makes any sensible difference in this Phae∣nomenon of the Experiment, the Aequilibrium being still constant to the same altitude of 27 digits, for the Mercury, and 32 feet for Water: yet, according as the Cavity of the Tube is either smaller, or greater, must the weight of the Liquors contained therein be either less, or more. Since therefore, we are to explore the definite weight of the Liquor contained, by the determinate Amplitude of the Tube containing; suppose we the Diametre of the cavity of the Tube to be one third part of a * 1.10 Digit, and we shall find the weight of the Quicksilver, from the base to the altitude

of 27 digits, to be near upon two pound, Paris weight: and upon conse∣quence the weight of Water in the same Tube, of 32 feet in altitude, to be the same; and the weight of the Cylindre of Aer, from its base incum∣bent on the surface of the restagnant Quicksilver, up to its top at the sum∣mity of the Atmosphere, to be also the same; otherwise there could be no Aequilibrium. Here, as a Corollary, we may add, that insomuch as the force of a body Attrahent may be aequiparated to the weight of another body spontaneously descending or attracted magnetically by the Earth: thereupon we may conclude, that the like proportion of weight appended to the handle of the wooden Sucker, may suffice to the introduction of an equal vacuum, in Galilaeo's Brass Cylindre.

But, perhaps, you'l object;* 1.11 that this seems rather to entangle then dis∣solve the Riddle. Since by how much the larger the cavity of the Tube, by so much the greater the quantity, and so the weight of the Quicksilver contained: and by how much the greater the weight, or force of the De∣priment, by so much the more must the Depressed yeild, and consequently, so much the lower must the Aequilibrium be stated.

To extricate you from this Labyrinth, we retort; that the cause of the Aequilibriums constancy to the point of 27 digits, whatever be the quantity of the Mercury contained in the Tube, is the same with that, which makes the descent of two bodies of the same matter, but different weights, to be Aequally Swift: for a bullet of Lead of an ounce,* 1.12 falls down as swiftly as one of 100 pound. For, in respect, that a Cylindre of Quicksilver contained in a Tube of a large diametre, doth not descend more swiftly, then a Cylindre of Quicksilver contained in a Tube of a narrow diametre: therefore is it, that the one doth not press the bottom, upon which as its Base, it doth impend, more violently then the other doth press upon its Base; and consequently, the restagnant Quicksilver about the larger Cylindre doth not, in its elevation or rising upward, more compress the Basis of the impendent Cylindre of Aer, then what is restagnant about the lesser Cylindre. Whereupon we may conclude, that a great Cylindre of Aer resisting a great Cylindre of Quicksilver, no less then a small doth resist a small: therefore ought the Aequilibrium be∣twixt the depressure of the Quicksilver, and the resistence of the circum∣stant Aer, to be constant to the altitude of 27 digits, aswell in a large, as a narrow Tube. Which reason may also be accommodated to Water and all other Liquors.

Notes

• * 1.1

  Art. 2. The Solution thereof in a Word.
• * 1.2

  Art. 3. Three praece∣dent positions briefly recog∣nised, in or∣der to the worthy pro∣founding of the mystery, of t••e Aers resist∣ing Compres∣sion beyond a certain rate, or determinate proportion.
• * 1.3

  Art. 4. The Aequipon∣derancy of the External Aer, pendent upon the surface of the Restagnant Mercury, in the vessel, to the Cylindre of Mercury re∣siduous in the Tube, at the altitude of 27 digits: the cause of the Mercuries constant sub∣sistence at that point.
• * 1.4

  Art 5. A convenient 〈◊〉〈◊〉, illustra∣ting and en∣forcing the same.
• * 1.5

  Art. 6. The Remain∣der of the Difficulty, viz. Why the Ae∣quilibrium of these two oppo∣site weights, the Mercury and the Aer, is con∣stant to the prae∣cise altitude of 27 d••g••t••: re∣m••ved.
• * 1.6

  Art. 7. Huma••e Per∣spicacity termi∣nated in the exterior parts of Nature, or simple Appa∣ritions: which eluding our Cognition, fre∣quently fall under no o∣ther compre∣hension, but that of ratio∣nal Conjecture.
• * 1.7

  Art. 8. The constant subsistence of the Mercury at 27 d••gits, ad∣scriptive ra∣ther to the Resistence of the Aer, then to any occult Quality in the Mercury.
• * 1.8

  Art 9. The Anal••gy betwixt the Absolute and Respective Ae∣quality of weigh••s, of Quicksilver and Water, in the different altitudes of 27 d••gits and 32 feet.
• * 1.9

  Art. 10. The definite weights of the Mercury at 27 d••gits, and Water at 32 feet, in a Tube of the third part of a digit in diametre; ••••und to be near upon two pou••d, Paris wei••ht.
• * 1.10

  Consul••ndus Mersennus, in tract. de Mensu∣ris & ponderi∣bus, cap 1. & 〈◊〉〈◊〉 physi∣comathemat. p. 229.
• * 1.11

  Art. 11. Quaere, Why the Ae∣quilibrium is constant to the same point of altitude in a Tube of a large concave, as well as in one of a small; when the force of the Depri∣ment must be greater in the one, then the other.
• * 1.12

  Art. 12. The solution thereof by the appropriation of the same Cause, which makes the de∣scent of two b••∣dies, of different weights, aequi∣velox.