STATICS. of the fmall pipe, at which the air paffes in our engine, out of the receiver into the pump: then covering this glafs with a great receiver, we luted it strongly to the engine, and, at the top, pour'd in as much water as fufficed to furround the internal receiver, if I may fo call it, and cover it to a pretty height. This done, we exactly closed, with a turn-key, the hole of the great receiver, at which the water had been pour'd in, that no air might pafs that way. And lastly, we began to pump out the air contain'd in the internal receiver; that the air, which, by the above-mention'd pipe, had communication with the external air, might no longer, by its preffure, affift the glass to refift the preffure which the incumbent and inclosed air, by virtue of its fpring, conftantly exercises upon the fubjacent water, and, by its intervention upon the fides and bottom of the internal receiver. At the firft exfuction, which could not be fuppofed to have well emptied the internal glafs, this veffel was, by the preffure of the fuperior air upon the furrounding water, broken into numerous pieces. The fame experiment, with a like fuccefs, was repeated with a ftronger internal glass.

Having squeez'd out of a moderately fized bladder the greatest part of its air, we tied the neck of it very clofe; and then, faftening to it a competent weight, we placed it at the bottom of the tallest and largest glass we could cover with our great receiver; that fo, tho' the incumbent air were pump'd out, none of the water might efcape with it, but ftill retain the fame height above the bladder. Having then pour'd upon the bladder as much water as would swim high above the upper part of it; we cover'd this glass of water with a great receiver, which being carefully cemented on to the engine, the pump was fet on work; and as the air which by its fpring prefs'd upon the furface of the included water, was by degrees pumped out; fo the air imprifon'd in the bladder, gradually expanded at the bottom of the water, as if no fuch liquor had interpofed between them, otherwise than by its weight; upon which account it must be allow'd a little to hinder the expanfion of the bladder, in proportion to the height it has above it. Thus the immerfed bladder was at length full blown, by the dilatation of the air inclosed in it; and, by its intumefcence, made a confiderable part of the water run over the fides of the glafs that before contain'd it all. And when access was given again to the external air, the internal being comprefs'd, the bladder was prefently reduced to its flaccid ftate.

We took a fmall fine bladder, whofe neck was ftrongly ty'd up, when it was about half full of air; this we put into a fhort brafs-cylinder, the lower of whose bafes was clos'd with a brass-plate, and the other left open; this open orifice we afterwards ftopp'd, but not exactly, with a cylindrical plug, that was fomething lefs than it, and was, by a rim at the top, hinder'd from reaching too deep into the cavity of the cylinder, that it might not damage the bladder which lay beneath it: upon the plug we placed a conical weight of lead; and this pile of feveral things, being fo placed upon our engine, that we could cover it with a great receiver, we care

fully cemented on, fuch a veffel, and at the top of it pour'd in fo much water STATICS. as would serve to fill the vacant part of the brafs-cylinder, and the cavity of the engine to fuch a height, that it covered all the leaden weight, which was feveral inches high, except a rim faftened to the top of it, for the conveniency of removing it. This being done, the pump was work'd; and, long before we had exhaufted the air of the receiver, that which was inclofed in the lank bladder had, by degrees, difplay'd so vigorous a spring that it raised up the weight, which lay upon it, to a confiderable height, and kept it there, till the air was let in from without, to affift its depreffure by the lead, which amounted to no less than about twenty-eight pounds.

We took a cylindrical copper-veffel, of a confiderable height; into this, being first almoft fill'd with water, we put a fquare glafs-vial, capable of containing nine or ten ounces of water, and exactly stopp'd with a cork, and a close cement, this vial, by a competent weight, was detained at the bottom of the water, from whofe upper furface it was confiderably diftant; then the copper-veffel, being placed upon the engine, and included in a great receiver, well cemented on; the air was, by degrees, pumped out: but, before it was quite exhaufted, the glafs, at the bottom of the water, was, by the fpring of the air included in it, burst into many pieces, not without great noife, and a kind of fmoke, or mift, that appeared above the furface of the water: and another glafs, of the fame fort, was broke, after the fame manner, in another veffel

Now, the confequence that naturally refults from the three last experiments, is, that fince barely upon withdrawing the preffure of the included. air, the air refiding in the immerfed bodies, did, by virtue of its spring, expand itself fo forcibly, and perform fuch confiderable things; the air above the water muft have exercifed a very ftrong preffure upon the furface of it; for, it must have been, at leaft, equivalent to that force of the immersed air, the exercife whereof it was able totally to hinder.

And, from hence, it may be eafily deduced, that the weight of the atmosphere acts upon bodies under water; tho' the interpofed liquor is vaftly heavier, in fpecie, than in air: for, we have juft now proved the preffure of inclofed air, which confifts in its fpring upon bodies under water. And, 'tis manifeft, that the ftrength of the fpring of this lower air, we make our trials with, is caufed by the weight of the upper, which bends and compreffes thofe little fpringy particles whereof our air confifts; fo that the weight of the atmosphere, being equivalent to the fpring of the lower air, muft prefs upon the furface of the fubjacent water, with a force equal to the fpring of that part of it which is contiguous to the water.

It has proved a great impediment to the reception of the doctrine of the Fluids prefs in weight and preffure of the atmosphere, that, if it could, really, exercife a different fo great a force as we afcribe thereto, it would, unavoidably, opprefs all manner from the bodies expofed to it: fo that neither men, nor other animals, would folids. be able to move under so great a load, or withstand its force.

STATICS. of the fmall pipe, at which the air paffes in our engine, out of the receiver into the pump: then covering this glafs with a great receiver, we luted it ftrongly to the engine, and, at the top, pour'd in as much water as fufficed to furround the internal receiver, if I may fo call it, and cover it to a pretty height. This done, we exactly clofed, with a turn-key, the hole of the great receiver, at which the water had been pour'd in, that no air might pafs that way. And lastly, we began to pump out the air contain'd in the internal receiver; that the air, which, by the above-mention'd pipe, had communication with the external air, might no longer, by its preffure, affift the glafs to refift the preffure which the incumbent and inclofed air, by virtue of its fpring, conftantly exercises upon the fubjacent water, and, by its intervention upon the fides and bottom of the internal receiver. At the first exfuction, which could not be supposed to have well emptied the internal glafs, this veffel was, by the preffure of the fuperior air upon the furrounding water, broken into numerous pieces. The fame experiment, with a like fuccefs, was repeated with a ftronger internal glass.

Having fqueez'd out of a moderately fized bladder the greatest part of its air, we tied the neck of it very clofe; and then, faftening to it a competent weight, we placed it at the bottom of the tallest and largest glass we could cover with our great receiver; that fo, tho' the incumbent air were pump'd out, none of the water might escape with it, but still retain the fame height above the bladder. Having then pour'd upon the bladder as much water as would fwim high above the upper part of it; we cover'd this glass of water with a great receiver, which being carefully cemented on to the engine, the pump was fet on work; and as the air which by its fpring prefs'd upon the furface of the included water, was by degrees pumped out; fo the air imprifon'd in the bladder, gradually expanded at the bottom of the water, as if no fuch liquor had interpofed between them, otherwife than by its weight; upon which account it must be allow'd a little to hinder the expanfion of the bladder, in proportion to the height it has above it. Thus the immerfed bladder was at length full blown, by the dilatation of the air inclosed in it; and, by its intumefcence, made a confiderable part of the water run over the fides of the glass that before contain❜d it all. And when accefs was given again to the external air, the internal being comprefs'd, the bladder was prefently reduced to its flaccid ftate.

We took a small fine bladder, whofe neck was ftrongly ty'd up, when it was about half full of air; this we put into a fhort brafs-cylinder, the lower of whose bafes was clos'd with a brafs-plate, and the other left open; this open orifice we afterwards ftopp'd, but not exactly, with a cylindrical plug, that was fomething lefs than it, and was, by a rim at the top, hinder'd from reaching too deep into the cavity of the cylinder, that it might not damage the bladder which lay beneath it: upon the plug we placed a conical weight of lead; and this pile of feveral things, being fo placed upon our engine, that we could cover it with a great receiver, we care

fully cemented on, fuch a veffel, and at the top of it pour'd in fo much water STATICS. as would ferve to fill the vacant part of the brafs-cylinder, and the cavity of the engine to fuch a height, that it covered all the leaden weight, which was feveral inches high, except a rim faftened to the top of it, for the conveniency of removing it. This being done, the pump was work'd; and, long before we had exhaufted the air of the receiver, that which was inclofed in the lank bladder had, by degrees, difplay'd fo vigorous a fpring that it raifed up the weight, which lay upon it, to a confiderable height, and kept it there, till the air was let in from without, to affift its depreffure by the lead, which amounted to no less than about twenty-eight pounds.

We took a cylindrical copper-veffel, of a confiderable height; into this, being first almoft fill'd with water, we put a fquare glafs-vial, capable of containing nine or ten ounces of water, and exactly stopp'd with a cork, and a close cement, this vial, by a competent weight, was detained at the bottom of the water, from whofe upper furface it was confiderably diftant; then the copper-veffel, being placed upon the engine, and included in a great receiver, well cemented on; the air was, by degrees, pumped out: but, before it was quite exhaufted, the glass, at the bottom of the water, was, by the fpring of the air included in it, burst into many pieces, not without great noife, and a kind of smoke, or mist, that appeared above the furface of the water: and another glafs, of the fame fort, was broke, after the fame manner, in another vessel

Now, the confequence that naturally refults from the three last experiments, is, that fince barely upon withdrawing the preffure of the included air, the air refiding in the immerfed bodies, did, by virtue of its spring, expand itself fo forcibly, and perform fuch confiderable things; the air above the water muft have exercifed a very ftrong preffure upon the furface of it; for, it must have been, at leaft, equivalent to that force of the immersed air, the exercife whereof it was able totally to hinder.

And, from hence, it may be eafily deduced, that the weight of the atmosphere acts upon bodies under water; tho' the interpofed liquor is vaftly heavier, in fpecie, than in air: for, we have juft now proved the preffure of inclofed air, which confifts in its spring upon bodies under water. And, 'tis manifest, that the strength of the fpring of this lower air, we make our trials with, is caused by the weight of the upper, which bends and compreffes thofe little fpringy particles whereof our air confifts; fo that the weight of the atmosphere, being equivalent to the fpring of the lower air, muft prefs upon the furface of the fubjacent water, with a force equal to the spring of that part of it which is contiguous to the water.

It has proved a great impediment to the reception of the doctrine of the Fluids prefs in weight and preffure of the atmosphere, that, if it could, really, exercife a different fo great a force as we afcribe thereto, it would, unavoidably, opprefs all manner from the bodies expofed to it: fo that neither men, nor other animals, would folids. be able to move under fo great a load, or withstand its force.

STATICS. of the fmall pipe, at which the air paffes in our engine, out of the receiver into the pump: then covering this glass with a great receiver, we luted it strongly to the engine, and, at the top, pour'd in as much water as fufficed to furround the internal receiver, if I may fo call it, and cover it to a pretty height. This done, we exactly clofed, with a turn-key, the hole of the great receiver, at which the water had been pour'd in, that no air might pafs that way. And lastly, we began to pump out the air contain'd in the internal receiver; that the air, which, by the above-mention'd pipe, had communication with the external air, might no longer, by its preffure, affift the glafs to refift the preffure which the incumbent and inclofed air, by virtue of its fpring, conftantly exercifes upon the fubjacent water, and, by its intervention upon the fides and bottom of the internal receiver. At the firft exfuction, which could not be fupposed to have well emptied the internal glafs, this veffel was, by the preffure of the fuperior air upon the furrounding water, broken into numerous pieces. 'The fame experiment, with a like fuccefs, was repeated with a stronger internal glass.

Having fqueez'd out of a moderately fized bladder the greatest part of its air, we tied the neck of it very clofe; and then, fastening to it a competent weight, we placed it at the bottom of the tallest and largest glafs we could cover with our great receiver; that so, tho' the incumbent air were pump'd out, none of the water might escape with it, but still retain the same height above the bladder. Having then pour'd upon the bladder as much water as would fwim high above the upper part of it; we cover'd this glass of water with a great receiver, which being carefully cemented on to the engine, the pump was fet on work; and as the air which by its fpring prefs'd upon the furface of the included water, was by degrees pumped out; fo the air imprifon'd in the bladder, gradually expanded at the bottom of the water, as if no fuch liquor had interpofed between them, otherwife than by its weight; upon which account it must be allow'd a little to hinder the expanfion of the bladder, in proportion to the height it has above it. Thus the immerfed bladder was at length full blown, by the dilatation of the air inclosed in it; and, by its intumefcence, made a confiderable part of the water run over the fides of the glass that before contain'd it all. And when accefs was given again to the external air, the internal being comprefs'd, the bladder was presently reduced to its flaccid ftate.

We took a small fine bladder, whofe neck was ftrongly ty'd up, when it was about half full of air; this we put into a fhort brafs-cylinder, the lower of whose bafes was clos'd with a brass-plate, and the other left open; this open orifice we afterwards ftopp'd, but not exactly, with a cylindrical plug, that was fomething lefs than it, and was, by a rim at the top, hinder'd from reaching too deep into the cavity of the cylinder, that it might not damage the bladder which lay beneath it: upon the plug we placed a conical weight of lead; and this pile of feveral things, being fo placed upon our engine, that we could cover it with a great receiver, we care