fon of their fallness, got up to the top of the water, with the more PNEUMATICS bulky and vigorous fort. And having, by letting in the air, forced up the water into the tube, we could not perceive that it afcended near the top, tho' the engine remain❜d unemploy'd for two or three nights together. Having, alfo, try'd a like experiment with quick-filver, inftead of water, in a tube about a foot and a half long; upon drawing down the quick-filver as low as poffible, and letting in the external air, we found, that some lurking particles of air were got up to the top of the tube, and hinder'd the quick-filver from rifing to that height again. And, tho' the mercury were, by this means, brought to appear as a very clofe cylinder; yet the air, in the receiver, being again evacuated, I could perceive feveral little bubbles faften'd to the infide of the tube, near the bottom. And, having purpofely watched one or two of the principal, I obferv'd, that tho' they grew gradually bigger, as the furface of the mercurial cylinder fell nearer to them; fo that, at length, they fweil'd to a confiderable bulk; yet, upon letting in the air, they did not break, but prefently fhrunk up, till they became invifible. Hence, it feems highly probable, that, even in the clofeft, and most ponderous liquors, and therefore, much rather in water, there may lurk undifcernible parcels of air, capable, upon the removal of the preffure of the atmosphere, and that of the liquor wherein it lurks, to produce confpicuous bubbles. From these feveral particulars, it feems plain, that the bubbles we have been treating of, were produced by fuch a fubftance, as may be properly enough call'd air; tho' we do not, pofitively, determine, whether air be a primogenial body, that cannot be generated, or turn'd into water, or any other body. This feems an important queftion, and might greatly conduce to explain the nature of the air. muted. Many naturalifts efteem the air to be ingenerable, and incorruptible; Whether air and plaufible reasons may be drawn, to countenance this opinion, from may be generathe permanency required in the corporeal principles of other bodies. Schotted, or tranf tus tells us, that, in the Mufæum Kircherianum, there is a glass, near half full of ordinary fpring-water, which, having been hermetically feal'd up by the famous Clavius, is, to this day, preferv'd not only clear and pure, but without, in the leaft, turning into air, tho' it has food for fifty years. Nor doth it appear, in thofe glaffes which are hermetically feal'd for chymical ufes, that the included air, during its long imprisonment, notwithstanding the alteration it receives from various degrees of heat, difcernibly alters its nature; whilft we plainly perceive, in digeftions and diftillations, that, tho' water may be rarified into vapours; yet it is not, really, changed into air, but only divided by heat, and diffufed into very minute parts; which, meeting together, prefently return to fuch water as they conftituted before. And even spirit of wine, and other fubtile and fugitive fpirits, tho' they readily fly into the air, and mingle with it, do yet, in the glaffes of chymifts, eafily refume the form of liquors. And fo volatile PNEUMATICS Volatile falts, tho' they will readily disperse themselves in the air, and play up and down the capacity of a receiver; yet, after a while, faften themselves to the infide thereof, in the form of falts. And the experiment made in our engine, with a piece of match, feems to fhew, that even thofe light and fubtile fumes, into which the fire itself fhatters dry bodies, have no fuch spring as that of the air; fince they were unable to hinder the expanfion of the air, included in a bladder they furrounded. Jofephus Acofta, indeed, tells us, that he faw, in the WeftIndies, fome grates of iron fo rufted and confumed by the air, that the metal crumbled between the fingers, was like parch'd ftraw. Varenius, alfo, tells us, that in the islands call'd Azores, the Air is so sharp, as, in a fhort time, to fret not only iron-plates, but the very tiles upon the roofs of houses, and reduce them to duft. But it may be faid, that these authors afcribe fuch effects, chiefly, to the winds; and that the corrofion of the iron may proceed not from the air itself, or any of its genuine parts; but from fome faline corpufcles difperfed thro' it, and driven, by the winds, against the bodies it is prefumed to fret. But, to try whether water could be turn'd into air, we fill'd an æolipile therewith; and placing it upon kindled coals, when the heat forc'd out a vehement ftream of aqueous vapours, we ty'd an empty bladder about the neck of it; and finding the æolipile, after a while, to blow up the bladder, we carefully ty'd it again, that the included fubftance might not get away. Then flipping it off from the æolipile, we convey'd it into our exhaufted receiver, and found, that the included substance expanded to a much greater bulk than before. And, having again taken out the bladder, we fuffer'd it to remain ty'd up till the next morning, when it appear'd little lefs tumid: but, upon repeating the experiment, I found it very difficult to make it fo accurately, as to fhew, that water may be rarify'd into true air. Ón the other hand, we found, by experience, that water, rarify'd into vapour, may, for a while, refemble the elaftic power of the air. For, if you fill a convenient æolipile with water, and lay it upon quick-coals, you may, after a while, observe so great a preffure of fome of the parts, contain'd in it, upon others; that the water will, fometimes, be thrown up into the air, above three or four feet high. And, if you then take the æolipile, almoft red-hot, from the fire, you may perceive, that the water will, for a confiderable time, be fpouted out in a violent ftream. And, if there remains but little water in the æolipile, when 'tis thus taken from the fire; immerfing the neck of it into cold water, you will find, that, after it begins to draw fome of it in, there will be generated, from time to time, many large bubbles in that water wherein the neck was plunged. These bubbles feem manifeftly to proceed from hence, that, for a while, the heat, in the æolipile, continues ftrong enough to rarify part of the water that is fuck'd in, and expel it, in the form of vapours, thro' that incumbent on the pipe. If, alfo, when the æolipile is almost full of water, you hold a fire-brand in that ftream of vapours which iffues out of the narrow mouth thereof, it will be very strongly blown with a confiderable noife. And it has been obferved, that, by placing the brand almoft at the mouth of the æolipile, the wind appear'd more vehement, than if it were held fome inches from it. The elaftic power of this ftream, indeed, feems manifeftly owing to the heat that expands, and agitates the aqueous particles thereof; and fuch rapid winds feem to be but water broke into little parts, and put in motion; fince, by holding a folid, fmooth, and clofe body against it, the vapours condenfing thereon, will prefently cover that body with water. But Kircher relates a remarkable experiment, which feems to fhew, that water is convertible into air. He tells us, that he made an hydraulic organ, which was fupplied with wind after the following manner. "There Fig. 35"was built a little chamber A H, five feet high, and three broad, with "two tranfverfe partitions CD, and EF, perforated like a fieve; under "these ran a pipe G, which carried the water that, by a ftop-cock, was "let out at H: the water, therefore, rufhing in violently at G, excited "a very great wind within; which bringing too much moisture along "with it, the partitions were contrived to purge it therefrom, that it might be convey'd more pure thro' the pipe A: but to render the air "ftill more pure, we made a fpiral tube of lead QR, and inferted it into the veffel S: by which means the air arrived at the organ, thro' the "orifice Z, as dry as if it had come out of an oven.' Now, if the wind that blows the organ here, doth not, upon the ceffation of its unufual agitation, gradually relapfe into water, I fhould ftrongly fufpect, that 'tis poffible for water to be eafily turn'd into air; for it can scarce feem probable, that fo little air, as is commonly contain'd in water, fhould be able, in fo fmall a quantity of water, as feems here employ'd, to make fo violent a wind as our author fpeaks of. I, therefore, fufpect that the wind, in this cafe, may be produced by fmall particles of the water itself, forcibly expell'd out of the chamber into the organ. And tho' no heat intervenes, perhaps, motion alone, if vehement, may fuffice to break water into very minute parts, and make them afcend upwards, if they cannot, otherwife, more eafily, continue their agitation. For, I remember, that betwixt Lyons and Geneva, where the Rhone is fuddenly ftraitned by two rocks, exceedingly near each other, that rapid ftream, dafhing, with great impetuofity, against them, breaks part of its water into fuch minute corpufcles, and gives it fuch a motion, that a mist, as it were, may be obferv'd at a confiderable diftance, arifing from the place, and afcending high into the air. But, it feems odd, that aqueous vapours fhould, like a dry wind, pafs thro' fuch a long winding pipe of lead, as that defcribed by our author; fince we fee, in the heads of ftills, and in the necks of æolipiles, fuch vapours are prefently, even by a very little cold, condenfed into water. We took a clear glafs bubble, capable of containing three ounces of water, with a long and wide cylindrical neck; this we fill'd with oil of vitriol, and fair water, of each almost a like quantity; and cafting in fix fmall PREUMATICS fmall iron nails, we ftopt the mouth of the glafs, which was now full of liquor, with a piece of diapalma, and fpeedily inverting the bubble, we put the neck of it into a fmall wide-mouth'd glafs, with more of the fame liquor in it; and as foon as the neck had reach'd the bottom of the liquor, there appear'd, at the upper-part of the vial, a bubble, about the bignefs of a pea, which feem'd rather to confift of new fmall bubbles, produc'd by the action of the diffolving liquor upon the iron, than any parcel of the external air, that might be fufpected to have got in upon the inverfion of the glass; efpecially fince we allow'd time to thofe little particles of air, which were carried down with the nails, to fly up again; and, foon after, we perceiv'd the bubbles, produc'd by the action of the menftruum upon the metal, afcending in fwarms to the former; and breaking into it, they foon exceedingly increas'd it, and, by degrees, deprefs'd the water, till, at length, the fubftance contain'd in thefe bubbles, poffefs'd the whole cavity of the vial, and most of its neck too; reaching much lower therein, than the furface of the ambient liquor, wherewith the open-mouth'd glafs was, by this means, almoft replenish'd. We fuffer'd both the vial, and the open-mouth'd glafs, to remain as they were, in a window, for three or four days and nights together; but often looking upon them, during that time, as well as at the expiration of it, the whole cavity of the glafs bubble, and moft of its neck, feem'd to be poffefs'd by air; fince, by its spring, it was able, for fo long, to hinder the expell'd liquor that furrounded it, from regaining its former place. And juft before we took the vial out of the other glafs, upon the application of a warm hand to the convex part of the bubble, the imprifon'd fubftance readily dilated itself, like air, and broke thro' the liquor in feveral fucceeding bubbles. Having alfo, at another time, made the like experiment, with a small vial, and nails diffolv'd in Aqua fortis, we found it fucceeded as the foregoing. And here we obferv'd, that the fteams newly generated, did not only poffefs almoft the whole cavity of the glafs, but feveral times, of themselves, broke away in large bubbles, thro' the ambient liquor into the open air; whence thefe experiments feem'd, manifeftly, to prove, that, in general, air may be generated de novo. And if, according to the mechanical hypothefis, the difference of bodies proceeds but from the various magnitudes, figures, motions, and textures of the fmall parts they confift of; there appears no reason why the minute parts of water, and other bodies, may not be fo agitated, or connected, as to deferve the name of air. 24. We chofe a glafs-egg, half an inch in diameter at the top, and an inch at the bottom; and filling it with common water, to the height of about a foot and a half, fo that the upper part remain'd empty, we enclofed it in the receiver; and, upon pumping, obferved bubbles at the bottom and fides of the glass; and, increafing as the air was drawn away, they, from time to time, plentifully afcended to the top of the water, where they quickly broke; but the widenefs of the glafs allowing them free paffage thro' the water, they did not, as in the former experiments, feem PNEUMATICS to make it fwell; and upon the return of the external air, the water appear'd to have loft of its firft extent, by the avolation of the air interfperfed. We put about two ounces of rain-water, carefully diftilled, into a round glass-bubble with a very small neck, which was thereby fill'd half way to the top, and then conveyed it into the receiver; and, tho' we drew out more air than ordinary, there appear'd not the leaft intumefcence of the water, nor any afcending bubbles. But fufpecting that either the fmall quantity of the water, or the figure of the veffel, might affect the experiment, we took the former glafs egg, and another, not much different from it, and fill'd the firft, with diftill'd rain-water, to the old mark, and into the latter, put a long cylinder of solid glass, to ftraiten the cavity of the neck; and then pouring fome diftill'd water into that alfo, till it reached near the top, they were both let down into the receiver: but here the air was fo far exhaufted, before there appear'd any bubble in either of the glaffes, that the difference betwixt this and common water, was very manifeft. But, at length, when the air was almoft quite drawn out, the bubbles began to disclose themselves, and to increase, as the preffure of the air, in the receiver, decreased. But, in the firft egg, the bubbles were very fmall, and never able to fwell the water above the mark; in the other, whofe neck was ftraitned, great numbers of large ones faften'd themselves to the lower-end of the folid piece of glass, and gather'd to fuch a degree, between it and the fides of the neck, that the water fwell'd a finger's breadth above the mark, tho', upon admitting the external air, it relaps'd to the former mark, or rather fell below it: upon which, all the bubbles prefently disappear'd in the former veffel; whilft feveral remain'd faften'd to the lower-part of the glafs cylinder, and continued there for above an hour after, but contracted in their dimenfions. And having fuffer'd these glaffes to remain above twenty-four hours in the receiver, we, afterwards, repeated the experiment; but tho' the receiver was carefully exhaufted, yet we fcarce faw a bubble in either of the glaffes; yet the water rofe the breadth of a barley-corn in the neck of that glafs wherein the folid cylinder had been placed; the liquor, in the other, not being fenfibly fwelled. And, laftly, upon letting in the air, the water in the ftraitned neck, foon fubfided to the mark, above which it had ftretched. The air con 25. We took a glafs egg, with a long neck, of about inch in diameter, and pouring in fallad-oil till it reach'd above half way to the top, we in- tain'd in oil. clofed it in the receiver, together with fome common water in a fimilar veffel. The pump being fet on work, there began to appear bubbles in the oil, much fooner than in the water; and afterwards they, alfo, afcended more plentifully in the former, than in the latter; and when the receiver was well exhaufted, the bubbles arofe almoft as numerous as ever: fo that none of the various liquors, we have try'd, feem'd to abound more with aerial particles, than this oil. And here 'twas remarkable, that between the time VOL. II. Kkk it |