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

CHAP. XXI. An Explication of Rarefaction.

IT being objected by the Author of a Book, De Corporum Inseparabilitate, that the Spring of the Air cannot be made out, whether we allow a Vacuum, or a Plenum. Waving the Forms which he lays his Objections down in, and a particular Answer to his Ways of Arguing, I shall take the following Method, to explain the Air's Spring. For supposing the Particles of the Air to consist of Matter, extended into thin Laminae, and those wound and folded up, like the Spring of a Watch; and that these Parts of Matter so wound up, are in a Continual Circular Motion, it will follow, that the Laminae in this Motion will en∣deavour to extend themselves, and to recede from the Axis or Center of their Motion, till hinder'd by the Opposition of each other, or some adja∣cent Bodies: and this Expansive Endeavour will be proportionably increas'd, as the Circular Mo∣tion of those Particles is quicken'd. And these Springy Corpuscles thus shap'd, and thus Me∣chanically mov'd, are sufficient to account for all that we ascribe to the Spring of the Air. For supposing the Diameter of those Parts of Matter next the Surface of the Earth, compress'd by the whole Weight of the Incumbent Atmosphere, to be 1/1000000000000 of an Inch,* 1.1 and to be represented by the Third Figure A B C D; it will Naturally follow, that Part of the Incumbent Weight of the Atmosphere, being taken off, they will expand

themselves so as to be 10/1000000000000 of an Inch in Diameter, as represented by E F G H. so that these Zones whirling round, will take up a space 1000 times bigger than before. And as from hence the Rarefaction of the Air is naturally accounted for; so the swelling of a Carp's Bladder, upon taking off the Pressure of the Atmosphere, is explain'd by the same Reason. And as the spon∣taneous Rarefaction of the Air is hence naturally explain'd, so it's Forced Rarefaction by Heat, is; for if the Particles of Heat penetrating the In∣terstices of these Aery Particles be in a violent rapid Motion, by increasing the Motion of the former Particles, they increase the Motion of the latter, and consequently strengthen their expan∣sive Virtue; And if these Rarifi'd Parts of Mat∣ter, by expanding themselves, leave larger In∣terstices betwixt their Laminae, they must conse∣quently be more pervious to the Rays of Light. So that granting this innate Motion in the Parts of Matter, and such a Configuration as I have mention'd, it naturally follows, that all the Phae∣nomena belonging to Rarefaction and Conden∣sation, may easily be explain'd by it.

* 1.2Nor will it be impossible to explain the Rare∣faction and Condensation, admitting of a Ple∣num, if we suppose with Cartesius, That the Air consists of Parts which are long, slender and flexible; for supposing with him, that these are whirl'd round by the Rapid Motion of the Glo∣buli Coelestes, those that lie next the Surface of the Earth, must needs be compress'd and hin∣der'd from that expansive Motion, more than those that have less Weight upon them; and consequently, when that Compression is taken

off, the expansive Force being encreas'd by it, they will consequently be expanded more Pow∣fully; and by whirling round, acquire longer Vortices: And for the like Reason the Air con∣tain'd in the Carp's Bladder, will extend it self when the Pressure of the External Atmosphere is taken off; and consequently, when the Exter∣nal Pressure is again admitted, those springy Parts being again compress'd are less able to maintain their new Vortices, but being wound up together again become more condens'd, that Pressure resisting the Force of their Spring. And as for the Reason why Water flows into the Re∣ceiver again in the Magdeburg Experiment, so impetuously; it hence evidently appears to pro∣ceed, from the Weakness of the Spring of the included Air, not being able to resist the more violent Pressure of the External; and for the same Reason likewise, the Carp's Bladder upon a reingress of that Air, is presently compress'd into its former Inconspicuousness.

* 1.3Nor will it be a less Piece of difficulty to ex∣plain the Aptness of Explosion in Gunpowder, by the Cartesian Hypothesis; for the Parts of that Combustible Matter of which it is made being shattered and broke into Pieces, consequently become more apt to be whirld about by the Materia Subtilis, and justling against each other, take up 1000 times as much space as before; and these Parts being thus agitated whatever Gun∣powder they fall upon, they presently shatter its Parts so as to put it in a Capacity to be agi∣tated by the Materia Subtilis: and consequently, the Globuli secundi Elementi, being expell'd out of the Place which contain'd the Gunpowder,

and the Parts of it being impetuously mov'd in that, they not only burst the Vessel they are con∣tain'd in, but drive every thing out of its Place which stands in their way, and is not able to re∣sist them.

Notes

• * 1.1

  See Plate the Second.
• * 1.2

  Rarefaction according to the Doctrin of the Ple∣nists.
• * 1.3

  Elasticity explain'd by the Carte∣sian Hypo∣thesis.