our Strength and Understanding, let us take a few into Confideration, in which the Great Creator and Ruler of the World has vouchfafed to reveal his Ways in fome measure to Mankind : And further, seriously reflect with our felves, whether they may not chearfully and undeniably ferve to convince a Mind defirous to know its Maker, that we have much more reason to acknowledge, in the Structure of the Universe, a Wife, Powerful, and Gracious Being, than the Skill of an Artificer from the most curious Machine that ever was produced by the Ingenuity and Workmanship of any Man whatever.

SECT. II. Firft of the Air.

To avoid Confufion, and obferve fome Order in the Contemplation of so many things, we fhall begin with those that are abfolutely useful and neceffary to the Prefervation and Well-being of Man; therefore we fhall treat of AIR, which is the principal of them all; and firft, of fome Properties thereof, and then of what Advantage and Service it is to Men, Beafts, Plants, and other Things; all which we shall briefly fhew in fome few Cafes.

SECT. III. The Gravity and Elafticity of the Air.

THE Diligence, or rather the good Fortune, of the Philofophers of the laft Age, has brought to light two remarkable Discoveries, and which were entirely a Secret to all the Ancients, touching the Conftitution of the Air; namely its Gravity or Weight, and its Spring, called in Latin by the Modern Naturalists, Vis Elaftica.

SECT. IV. An Experiment concerning the Gravity of the Air.

FOR fome thoufand Years the Air was esteem'd to be a Body fo light, that it would never defcend like other Bodies, till the Invention of Barometers gave the first hint to Mankind, that the Air might likewise be a heavy Body.

And how greatly the Experiment of thefe Weather-Glaffes has contributed to the chief Proofs of the Gravity of the Air, may be seen by the Sufpenfion of the Quickfilver in those Tubes in many Cafes, which is to be afcrib'd, first to its Elaftic Faculty, and afterwards to its Gravity, which caufes the faid Faculty to exert itself; as will appear by what follows.

Wherefore, in order to prove directly the Gravity and Weight of the Air, this Method seems to afford the ftrongest Proof, or at least the cleareft and fimpleft: Take a Glafs full of Air, and weigh it in a nice and exact Pair of Scales; then drawing out the Air as far as poffible with an Air-Pump, and weigh it again, you will find that it was fenfibly heavier before the Air was exhaufted than it is afterwards. The hollow Glafs Balls which are commonly fold with the great kind of Air-Pumps, are very proper for fuch an Experiment, and bigger Glaffes are yet more fo.

I find in my Notes, that fuch a Ball or Bubble had loft with its Air, fixty two Grains of its Weight, which is more than fufficient to convince us of the Gravity of the Air. According as we make ufe of bigger or fmaller Bubbles, this Difference will appear greater or lefs.

SECT.

SECT. V. and VI. The Air's Elaftick Faculty, proved Experimentally.

THE Second Property, for the Knowledge of which we are beholden to the Difcoveries of later Years, is the Elaftick Power or Springiness of the Air; whereby its Parts, like Steel Springs that are bent with Force, do continually endeavour to expand themselves; and fo by their Separation from each other, to take up a larger Space, driving away and preffing on every Side, all that makes any Refistance to them.

To prove this, many Experiments have been made by the Famous Boyle and others. The common Method of fhewing it is by a little Bladder E (Tab. XIII. Fig. 1.) which is about as big as a large Goofe Egg, when full blown. Squeeze the Bladder fo as to leave but a very fmall quantity of Air in it: Then having tied the Neck clofe, hang it up by its String to the little Hook D, of the Glafs Receiver A B C, which being laid on the Plate of the Air-Pump B A, if you exhauft the Air from the Receiver at F, which pafs'd on the outfide of the Bladder, the Spring of the Air in the Bladder will exert it felf fo, that the Bladder will fwell as if it was ftrongly blown up with a Pipe.

And for a further Proof of this Elaftick Power of the Air, feveral other Experiments, hereafter quoted in the proper Places, may be ferviceable.

SECT. VII. The Preffure of the Air.

Now that Operation or Effe&t which the Air has upon other Bodies, by this its Weight joined to the Expanding or Elaftick Force of its Parts, is what the Moderns call the Preffure of the Air: The

The furprifing Strength of which is incredible to many, and the Properties in its Ufes no other than wonderful.

SECT. VIII. The Miftakes of fome Atheifts.

Now before we proceed any farther, let us answer these Men, who to defend their unhappy Notions, viz. That there is not much Wisdom requifite in the Direction of many Things about them, alledge, That most of thofe Things are either entirely at reft, or at least mov'd but very flowly, and think this a strong Argument for their Affertions, because when things are fuppos'd to be without Motion, there does not feem much Wifdom not Power neceffary to continue them in the State in which they are; because a flow and languid Motion is known not to want fo much Force and Direction to prevent its doing Mischief, as that Motion which has more Velocity and Strength in it: And if this laft be allow'd, the firft carries a great deal of Probability with it, at least in the Minds of ignorant Perfons: For feveral People fitting in a Chamber, for inftance, are not fenfible of any Force upon them from Powers operating externally; the Glafs of the Windows, that is known to be fo brittle, remains in the fame Condition; the Tapistry or Hangings of the Room immoveable; not a Hair of their Head ftirs; in fhort, every thing feems to them plainly enough to be in perfect Reft. Let 'em go abroad, and unless the Air be put into Motion by Winds or Storms, they meet with no violent Oppofition, but every thing feems ftill and calm to them, excepting perhaps fome uncommon Revolution or Changes, which, because they cannot eafily trace the Causes, feem to be merely fortuitous; from whence they conclude, that at

fuch

fuch times they are Safe and Secure enough, and ftand in need of no greater Power than they themselves are able to furnifh for their own' Defence.

This Miftake does oftentimes render the unhappy Atheists very eafie for a while, and makes them flatter themselves, that there is nothing about them which they need to fear. But in order to' excite different Thoughts in them, and to make them apprehend Matters as they really are; let them go on and Contemplate with us thofe great and terrible Powers, which, even at the very time that they think themselves to be in the fureft Calm and Stillnefs, move continually round about them, and they continually live in the midft of 'em ; which Powers, if they were not most wonderfully reftrained by an Equilibrium or Balance, (and fo hinder'd from hurting us, and thereby only ren der'd infenfible) would be able, as foon as ever that Equilibrium ceafed to operate, in an inftant of Time to crufh us into Atoms.

SECT. IX. A Defcription of the Barometers; and an Experiment of the Preffure, and of the Weight of the Air thereby.

Now to the end that this may not appear to any one more marvellous than true; take a Glafs Tube AO (Tab. XIII. Fig. 2.) of about three Foot in length, and of the bignefs of a Goose or Swan's Quill, clofed at A and open at O; let it be filled with Quickfilver; then stopping the Orifice with your Finger, turn it down into another Veffel of Quickfilver, as defcribed here in the Glass BOD; then drawing your Finger away, the Quickfilver that is in the Tube will have an opportunity of finking down, fome of it running to the other that is in the Glafs. But it

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is