THE PREFACE Neumatics is that part of universal philosophy, which confiders the properties, the ufe, and effects of the air; the fluid we breathe, and which is abfolutely neceffary to maintain the life of animals. This is a fubject, therefore, that cannot but be highly useful to inquire into: and berein Mr. Boyle appears to have exercifed himself more than any pbilofopher before his time or fince. Indeed, the antients had no notion of this part of philofophy; and Jeem to have never dream'd of an engine wherewith to draw the air from veffels, and prevent its return into them. Otto Gueric, the famous conful of Magdeburg, first, unless we except Friar Bacon, bit upon an expedient to do it; and from a hint of this it was, that Mr. Boyle, improving on the defign of the conful, originally contrived his air-pump: a machine, to which we are indebted for the folution of many phenomena in nature; and momentous discoveries in the fluid, which of all external ones, feems to be the most familiar and useful to us. Aman of an ordinary capacity, poffefs'd of fuch an engine as this, would have been perplexed to know what ufe to make of it; but fuch a genius as Mr. Boyle, could not but apply it to noble and ferviceable purposes. In veffels of glass, emptied of air by its means, be foon included a great variety of proper fubjects, one after another; of which he had before-hand wrote down a long catalogue. And as this engine was at firft imperfect, but afterwards received confiderable improvements, at different times, I am induced to let all the experiments made with it by Mr. Boyle, ftand in the order wherein he wrote them, rather than to range them under feveral beads. For thus they give the history of the air-pump and its improvements from time to time: but if the other method had been taken, the advantage of these experiments must have been loft in their historical capacity; which would prove a greater inconvenience than the feeming diforder wherein they now occur: especially confidering, that this may easily be remedied, by means of the index. Numerous are the experiments made by Mr. Boyle, with this engine; but ftill there may be fomething left for future pbilofophers to do with it, befides repeating, varying, and confirming his trials. The air-pump, as 'tis now made, has many advantages over even the best which was employ'd by Mr. Boyle: it is fo much more manageable, commodious, and exact, (especially as improved by that excellent mechanic, Mr. Hauk fbee) its apparatus is fo well fuited for all exigencies of experiments; and the whole comes on fuch eafy terms, in comparison of what it coft our generous philofopher, that if it were only to be witness of the furprizing dif coveries be made with it, 'tis pity any well-wisher to philofophy should be without it. But were this inftrument in more general ufe; and would men of invention fet themselves to contrive new experiments for it, who knows what farther light it might afford us; and in producing how many other effects of nature, the air would appear to be concern'd? The late Mr. Haukfbee made feveral experiments with it, which, perhaps, Mr. Boyle himself never thought of; tho he evidently contrived a large number; which, for want of a fit opportunity, convenient glasses, and ther apparatus, he could never fee the event of. The subject, therefore, appears far from being exhaufted: the air-pump is a fruitful engine, and feems fitted to examine almost all the productions of nature: and there are many things in philofophy that cannot be done without it. 'Twas this which lately open'd a new field of Knowledge, and greatly affifted Mr. Boyle to introduce or revive the mechanical philofophy; this evidently help'd to overthrow the doctrine of nature's dread of a Vacuum, by which the modish philofophy of his time, falsely accounted for abundance of phenomena; to this is owing the greatest part of those noble experiments, which appear under the following bead of Pneumatics; and laftly, to this we owe fome furprizing difcoveries of Sir Ifaac Newton, and a great bare of the prefent fyftem of philofophy. TH Phyfico-mechanical EXPERIMENTS, To fhew the Spring and Effects of the AIR. T SECT. I.. HE air is fo neceffary to life, that most creatures which The origin of breathe cannot fubfift for many minutes without it; and most the air-pump. of the natural bodies we deal with, being, as well as our own, almost perpetually contiguous to it, the alterations thereof have a manifeft fhare in many obvious effects, and particularly in diftempers; wherefore a farther inquiry into the nature of this fluid, will probably fhew, that it concurs to exhibit abundance of phenomena, wherein it has hitherto feem'd little concern'd.. So that a true account of any new experiment, upon a thing whereof we have fuch a.conftant and neceffary ufe, may prove advantageous to human life. With this view, before ever I was inform'd that Otto Gueric, the ingenious conful of Magdeburg, had practifed a way in Germany of emp tying glafs veffels of the air, I had made experiments on the fame foundation; but as that gentleman firft produced confiderable effects by this means, I acknowledge the affiftance and encouragement which the report of his performances afforded me. But as few inventions happen to be compleat at the firft, fo the engine employ'd by the conful, feem'd very defective in its contrivance; whence but little more could be expected from it, than thofe very few phenomena obferved by the author, and related by Schottus. I therefore put Mr. Hook upon contriving an air-pump, more manageable and convenient, that might not, like the German-engine, require to be kept under water; and after fome unfuccefsful attempts, he fitted me with one, confifting of two principal parts, a glass veffel, and a pump to evacuate the air. The PNEUMATICS Fig. 30. The air-pump defcribed. The first is a glass A, with a large mouth, a cover thereto, and a ftopcock fitted to the neck below. This would contain 30 quarts of water. B C, the mouth of it, is about four inches in diameter, and furrounded with a glass lip, almoft an inch high, for the cover to reft on; wherein DE, is a brafs ring, to cover, and be cemented on to the lip BC. To the internal orifice of this ring, a glafs ftopple is fitted, to keep out the external air. In the middle of this cover is a hole H I, half an inch in diameter, incircled with a ring, or focket; to which is adapted a brass stopple K, to be turned round, without admiting the leaft, air. In the lower-end of this, is a hole 8, to admit a ftring, 8, 9, 10; which alfo paffes thro' a fmall brass ring L, fixed to the bottom of the ftopple F G, to move what is contained in the exhausted veffel, or receiver. That the flopcock N, in the first figure, might perfectly exclude the air, we fastened a thin tin-plate, MT VW, to the shank, of the cock X, all along the neck of the receiver, with a cement made of pitch, rofin, and wood-afhes, poured hot into the cavity of the plate; and to prevent the cement from running in at the orifice Z, of the shank X, it was ftopt with a cork fixed to a ftring, that it might be drawn out at the upper orifice of the receiver; and then the neck of the glafs, being made warm, was preffed into the cement, which thus filled the interstices betwixt the tin-plate and the receiver, and betwixt the receiver and the fhank of the cock. The lower part of our engine confifts of a fucking-pump, fupported by a wooden frame, with three legs 111, fo contrived, that, for the freer motion of the hand, one fide of it may ftand perpendicular; and a-crofs the middle of the frame we nail'd a piece of board 222, to which the principal part of the pump is fixed. The pump confifts of an exact strong concave cylinder of brafs, fourteen inches long, its cavity three inches in diameter; to which a fucker, 4455, is adapted, made up of two parts; one of which 44, is lefs in diameter than the cavity of the cylinder, with a thick piece of tann'd leather nailed on it, whereby it excludes the air. The other part, a thick iron plate 55, is firmly joined to the middle of the former, and is a little longer than the cylinder; one edge of it being fmooth, and the other indented, to receive the teeth of a small iron-nut a By, fixed by two staples to the underside of the board nailed a-cross 22, on which the cylinder ftands; and is turned by the handle 7. The laft part of the pump is the valve R, a hole at the top of the cylinder, and taper towards the cavity; to this is fitted a brass-plug, to be taken out as occafion requires. The engine being thus contrived, some oil must be pour'd in at the top of the receiver upon the ftop-cock, to fill up the interftices of its parts, and that the key S, may turn with the greater eafe. A quantity of oil, alfo, must be left in the cylinder, to prevent the air from getting betwixt that and the fucker; for the like reafons, fome muft, likewife, be applied to the valve. And here it is proper to obferve, that when we ufed oil, or water, feparately, for this purpofe, and they have not answered the end, a mixture of the two has afterwards proved effectual. And, that the air may not PNEUMATICS enter betwixt the brafs-cover and the ring, 'twill be convenient to lay fome diachylon plaifter on their edges with a hot iron. That no air, also, may remain in the upper part of the cylinder, the handle is to be turn'd till the fucker rifes to the top; and then, the valve being fhut, it is to be drawn down to the bottom; by which means, the air being driven out of the cylinder, and a fucceffion from without prevented, the cavity of the cylinder must be empty of air; fo that when the ftop-cock is turn'd to afford a communication betwixt the receiver and the cylinder, part of the air before lodg'd in the receiver, will be drawn down into the cylinder; which by turning back the key, is kept from entering the receiver again, and may, by unftopping the valve, and forcing up the fucker, be driven into the open air; and fo, by repeated exfuctions out of the receiver, and expulfions out of the cylinder, the veffel may be exhaufted as the experi ment requires *. The air-pump has receiv'd great improvements fince the time of Mr. Boyle, and feems brought to its utmoft degree of fimplicity and perfection, by the late, and the prefent Mr. Hauksbee. This inftrument, as 'tis now made, by Mr. Hauksbee, conFig. 31. fifts of two brafs-cylinders, a aa a, twelve inches high, and two their internal diameter. The emboli are raised, and depreffed, by turning the winch bb, backward and forward. This winch is fasten'd to a fpindle, paffing through a lanthorn, whofe pins ferve for cogs, laying hold of the teeth of the racks cccc; fo that one is depreffed, and the other elevated reciprocally. By this means the valves, made of limber bladder, and fix'd on the upper part of each embolus, and at the bottom of the cylinders, mutually exhauft and difcharge the fame air from the receiver: which becoming nearly empty, the preffure of the external air on the defcending embolus is fo great, that the power required to raise the other, need but little furmount the friction of the moving parts; whence this pump becomes preferable to all others. The bottoms of the barrels lie in a brafs difh dd, its fides two inches high, containing water to keep the leather-collars, on which the cylinders ftand, moitt; whereby the air is precluded. The cylinders are fcrew'd hereon by the nuts eeee, which force the frontispiece ff, down upon them; thro' which pass the two pillars gggg. Each pillar has an iron VOL. II. 1. Upon belonging to it, paffing from them in the Ggg the |