ing? In which fo vifibly appear the great Designs of GOD in making the Seas and other Waters capable of bearing fuch mighty Burthens, at the fame time that they are composed of a Matter that may be separated and exhaled by the fmalleft Force of the Sun, or any other Warmth, and drawn up into the Air, and turned into Clouds and Vapours.

SECT. LXV. Lateral Preffure, and the Benefit

thereof.

Now as the Wonders of the Preffure of Fluids upwards and downwards, are calculated to render Mankind happy, fo likewife may this fame Law of Preffure according to Depth (by which the lateral Preffure is alfo regulated) ferve for a great Proof particularly; becaufe without the fame, the Sea would be unnavigable for Ships, and the Earth in a great Measure uninhabitable, fo that many well-peopled Countries would have nothing to expect but the utmost Destruction. Let it be fuppofed for Inftance (Tab. XXIX. Fig. 5.) that the Sea BCDE ftands at the Height BC against the Dyke A C M N; and first that the Water being moved by no Winds, there lies a Ship still at IFK, and at the fmall distance BH from the Dyke: Now 'tis plain, that if Fluids were governed by no other Laws than folid Bodies, the little Water at AH F being much less in Quantity, and therefore in Force and Gravity, the Ship would be thrust by the greater Quantity of SeaWater E G F, towards the Dyke A B; according to which manner it would not be able to lie ftill in any part of the whole Sea, without being preffed by the heaviest and greatest Quantity of Water towards the fide of the fmalleft and lighteft. We don't take any notice here of the Obliquity of fuch Preffures. Now

Now what Inconveniencies would occur from the failing upon the Sea and other Waters, if the fame fhould exert their Preffure not according to the fimple Laws of Depth, but like folid Bodies, according to their Quantity and Surface alfo ?

But that which we now have chiefly in view is, what Dykes at ACM N would Men be obliged to make, if they were to be oppofed against the lateral Preffure of the whole Sea C D E B, if the Force thereof were only regulated according to the Surface and Quantity of the Water that preffed upon the Dyke, as it happens in folid Bodies, had it not pleased the Director of all Things to fubject the Force of this lateral Preffure fo ftrictly to the fingle Height or Depth of the Water, and not to its Breadth and Quantity; infomuch that altho' the whole Sea fhould press against one Dyke at BC, the faid Dyke would bear no greater Burthen than the Preffure of that little Water which (fuppofing CL to be equal to B C) could only be contained in the Space B C L, according to what we have already fhewn above?

SEC T. LXVI. Convictions from the fame.

Now can any one fee exerted fuch a Law of fo many Millions of fuch exceeding fmall Particles of which the raging Ocean is compofed, and which have not the leaft Knowledge of what they are doing, and yet act with fo much Nicenefs at all Times, and upon all Occafions; and cannot he therein discover an over-ruling Wisdom and Power? The rather, fince this Law is the only Means by which fuch a dreadful Collection of Waters is hindred from overflowing the dry Land, whilft the Dykes refift their whole Force, fo that neither Men nor Beafts are overwhelm'd in the lower Grounds; of all which one cannot think without Emotion

Emotion and Horror, when one reflects upon the Weakness of the faid Dykes, with refpect to the unconceivable Weight and Quantity of the Water that preffes against them.

If now any living Man had found out the Secret of obliging the whole Sea to fubmit itself to fuch Laws, that how vaft foever it was, but a very fmall part of it fhou'd prefs upon the Dykes, would not an Atheist stand aftonished at his Wifdom? And if he had invented a Method, whereby not only all Waters, but likewife the whole Ocean of Air furrounding the Globe of the Earth, and all other fluid Matters, even to the smallest Particle of them, could be bound and fubjected thereto; would not an Atheist be again obliged to confefs the unconceivable Extent of his Power?

CONTEMPLATION XXVII. Of fome CHYMICAL LAWS of Nature.

SECT. I. Tranfition to other Laws.

FTER having contemplated those Laws which have long been, and particularly of latter Years are become the Objects of Mathematicians, let us now pafs on to another kind of Laws of Nature, which do not feem to be performed fo much by plain Percuffions or Strikings, as many of the firft, but according to other Rules (we fay feem, because we acknowledge ourfelves ignorant of the manner thereof) by which Things being placed at a certain Distance from

each

each other,are attracted (or at least do move) towards one another, without any vifible Discovery of Percuffion or Striking of other Parts there prefent ; or elfe fuch, as being placed in certain Circumftances by or near other Bodies, are driven away, or feparated from one another; to which Actions the Learned have annex'd the Terms of Attraction and Repulfion; to which Laws the great Dire&or has bound thofe Bodies that obey the fame, after a manner hitherto more wonderful than intelligible; and as the Naturalifts have discovered the former Laws by Experiments, fo the Chymifts in a great measure have found out thefe, which likewife have lately become the Objects of Mathematical Contemplations.

SECT. II. Experiments fhewing the Operation of
Acids and Alcalies.

THE great Phenomenon of Nature, and which has given a Handle to many Difputes and Argumentations of Chymifts and other Philofophers, is the famous Effects produced by Acids and Alcalies. By this laft is understood every thing that ferments or boils up when mingled with foure Bodies, and afterwards is intimately united to the fame. Those who have never feen the A&tion refulting from the Mixture of Acids and Alcalies, would be wonderfully furprised thereat; and they may easily make the Experiment, by putting in a little beaten Crabs Eyes, which is the Alcali, into Vinegar, which is the Acid, and they will prefently fee the Effects thereof.

But the Motion will be much more violent, if one mixes the Filings of Iron with the Acid Spirit of Salt-Petre or Aquafortis, and attended even with a great Heater.

To

To fhew this Effervefcence in Liquids, we may take Spirit of Sal Armoniac mixed with melted Pot-Ah, or Solt of Tartar, in Water, and mix it with the Acid Spirit of Salt, Salt-Petre, or Vitriol, and we shall presently discover a frong Effervefcence between them.

SECT. III. The aforefaid Salts are changed and unîted by Effervefcences.

Now how many Effects refult from thefe Effervefcences, has been often fhewn experimentally by the Chymifts.

It is a common Confequence, that after these Motions both the Acids and Alcalies lose their former Properties, or at least do frequently feem to lose them, such as their Tafte and Sharpness, and being closely united to each other, do thereby produce a third Conftitution entirely different from each of the former, fuch as what the Chymifts call a Salfum, Enixum, Muriaticum, Neutrum or Mixtum, or as we call them in our Language, a fatiated, a Pickle Salt, or a mingled Salt, all proceeding from a Mixture of Alcaline-Salts, as Pot-Afb, or Volatile Salts with an Acid.

SECT. IV. Experiments, fhewing that Acids and Alcalies precipitate, or are feparated from each other.

BESIDES this, when fome of the faid Alcalies. and Acids already united with each other, and, as they term it, are fo far fatiated, that they will not act any longer upon others of the fame Kind, and adhere so closely to the former, that it would be very troublesome to feparate them again without the Addition of other Matter, and in fome Cafes even impoffible to do it at all; Trials of the Operations of these Salts upon one another, have VOL. III.

Qqq

taught