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tain'd, i. e. to fell, its Weight ceafes to make a Part of that of the Fluid; which by this means becomes lighter. Thus, adds he, the watery Vapours, while fuftain'd in the Air, increafe its Weight ; but when let fall, ceafe to weigh a- long with it. Thus the Weight of the Air is diminifh'd ; and thus the Mercury falls, and Rain enfues.

But M. Zeiinita'i Principle, notwithstanding the Expe- riment he brings to confirm it, is falfe, as has been made appear by a counter-Experiment of Dr. 2)efaguliers. For, a Body, whether specifically equal, or lighter, or heavier than a Fluid, while it is immerg'd in it, whether it be at Rell or in Motion, adds to the Fluid a Weight equivalent to that of an equal Bulk of the Fluid ; as follows from that Law in Hydroftaticks, 'that Fluids gravitate according to their perpendicular Altitudes. However, were M. Leibnitz's Principle true, yet 'tis defeflive ; and that in the fame rc- fpect with Dr. Halley's : Nor wou'd it account for the Pha:- nomena more than the other. For, fuppofing the Vapours, by being condens'd, to be put in a Motion downwards, and fo ceafing to gravitate with the Atmofphcre ; they will therefore fell, till they reach a Part of the Jtmofphere of the fame fpecifick Gravity with themfelvcs ; and there they will hang as before. If the Mercury fall, 'twill only be during the Time of that Defcent; for thefe once fix'd, the former Gravity is retriev'd; or, were it not retriev'd, yet no Rain wou'd enlue the Fall of the Mercury.

If it might be allow'd us to add any thing after thefe great Men, it mould be as follows : 'Suppofe any Number of watery Veficles, v.g. a Million, floating in any Part of the Jtmofphere, over any determinate Portion of the Globe ; for inltance, over A B. If the upper Veficles be condens'd by the Cold of the upper Regions, their fpecifick Gravity will be increas'd, and they will defcend; the Ho- rizontal Clafs i v.g. to 2, 2 to 3,JSfc. where meeting with other Veficles not yet pre- cipitated, they will coalefce, or run into larger Veficles, by the known Laws of At- traction. Or, if we rather chufe to have the Wind aft, let it drive either horizon- tally, or obliquely : In the former Cafe, the Veficles, Clafs 8, will be driven a- gainft p ; that, againft io, &c. or the oblique Clafs A 7, driven againft 5, 8 againfl 4, JjY. By this means likewife will the Particles coalefce, and term new and larger Veficles, as before ; fo that their Number, which before was a Milli- on, will now be reduced, v.g. to a Hundred Thoufend : But by the fame Coalition whereby their Number is diminifh'd, their fpecifick Gravity is increas'd, ;'. e. they come to have more Matter in the fame Space, or under the feme Sur- face ; as may be eafily prov'd from Principles of Geometry : For, in augmenting the Mafs of any homogeneous Body, the Increafe of Surface does not keep pace with that of the Solidity; but that of the former, is as the Square of the Diameter ; and that of the latter, as the Cube of the fame. If then the Diameter of a Veficle were 4, and its Surface and Mafs 24 ; after Coalition, if its Diameter be 6, its Surface or Bulk will be 54, and its folid Content 81. Butfince the femcQuantity of Matter is now inalefs Space, or under lefs Dimenfions, it will lofe lefs of its Weight by the Rcfiftancc of the Medium. This is evident ; for, a Body immerg'd in a Fluid, lofes nothing of its Weight, but by the Friction of its Parts againft thofe of the Fluid ; but the Fridion is evidently as the Surface : therefore, where the Surface is leflen'd, the Refiftance muft be fo too. Con- fequently, the Veficles, whofe Gravity before the Coalition was equal to the Refiftance of the Medium, now that Re- fiftance is diminifh'd, will defcend ; and that with a Velo- city, in a Ratio of the Increafe of the Mafs to the Increafe of the Surtace. In their Defcent, as they arrive at denfer Parts of thaAtmofphere,v.g.s,t 4, 5, tfc. their Mafs and Sur- face again will be increas'd by new Coalitions ; and thus, by conftant frefti Acceffions, more than equal to the con- itant Refiftances, they will be enabled to purfue their Tour- ney thro all the Stages of the Air, till they reach the Earth ; their Maffcs exceedingly magnified ; and in the form of Rain.

Now that the Vapours are got down, let us confider how the Barometer muft have been affected in their Paffagc. E er any of the Veficles began to fubfide.either from the Ac- tion of the Cold, or of the Wind, they all floated in the Por- tion of the Jtmofphere A B C D, and all gravitated towards the Centre E Here now, each refpeffively refiding in a ft" of .,*f Medium of the feme fpecifick Gravity with it felf, will lofe as much of its Weight, as is equal to that Ct a Part of the Medium of the feme Bulk with itfelf Weight each lofes, it communicates to the Medium, which now preflis on the Surface of the Earth AB, with 'its own Weight, and that of the Veficles conjointly. Suppofe then, this united Preffure keeps up the Mercury in the Barometer at 30 Inches : By the Coalition of the Veficles from the
 * '. e. each will lofe all its Weight. But then, whatever

Caufes aforcfaid, their Surfaces, and confequehtly their Friction is leflen'd: They will therefore communicate lefs of their Weight to the Air, i. e. lefs than the whole ; and confequently will deicend with theExcefs, /'. e. with a Ve- locity equal to the Remainder, as before obferv'd. Now as the Veficles can afl no otherwife on the Surface of ihe Earth AB, but by the Mediation of the interjacent Air- in proportion as their Affion on the Medium is lefs.thcir Action on the Earth will be lefs. 'Tis alfo evident, that the Sur- face of rhe Earth A B, muft be now lefs prefs'd than before - and that in proportion, as the Veficles referve more of their Weight uncommunicated to the Medium, to promote their own Deicent, i. c. in proportion to the Velocity of the fall- ing Veficles; which is, again, in proportion to their Bulks Thus, as the Veficles deicend ; their Bulks continually in- creafing, the Friaion, and therefore the Preffure on the Earth, and laftly, the Height of the Mercury, will conti- nually decreafe, during the whole time of the Fall. Hence we fee, both why the Veficles, when once Beginning to fall perfevere ; why the Mercury begins to feudal the fame time ; and why it continues and ceafes to fell together with 'em : which were the great Defiderata in the Philofo- phy of the Barometer.

I fee but one Objection that lies againft this Theory - and 'tis this, That the Veficles being put in Motion aiid' ftriking againft the Particles of the Medium and one ano- ther with feme Moment, will meet with a considerable Re- fiftance from the Vis Inertia thereof; by which means their Defcent will be retarded, and the Preffure of the Jtmo- fphere retriev'd ; the Impetus of the moving Veficles being fuppofed to compenfate for their Lofs of Surface. Thus a heavy Body, fuftain'd in a Fluid by a Hair, and moved up and down therein, preffes more on the Bottom, than when held at Reft ; which additional Preffure will be the greater as the Velocity of the felling Veficles is the greater • a greater Impulfe being requir'd to break thro the. Vis Inertia of the contiguous Particles, in a lefs time than in a larger But we have both Reafon and Experiment againft this Ob- jection ; For befides that the Velocity of the Veficles in thefe Circumftances muft be very (malt, and their Impulfe inconsiderable; befides, that the Vis Inertia of the Air muft be exceedingly weak, by reafon of its extreme Sub- tility; and that it muft be a very improper Vehicle to con- vey an Impulfe to a Diftance, by reafon of its Elafticitv- wefind, that even ,n Water, f> grofs un-elaffick Medium) and a Piece of Lead, (a ponderous Body which fells with a great Moment) that even here the Body, in its Defcent thro the Fluid, gravitates confidetably lefs than when fuf- taind at Reft therein: In which the feveral Experiments ot Reaumer, Ramazzini, and -Dcfaguliers, all aoree

BARON, a Term ufed in various Senfes : Firft' a s a Degree of Nobility next below a Vifcount, and above a Gentleman ; in which Senfe it is the fame as in other Na- tions, where Baronia are -Proving; and Barons are I ■ Vu ha, ve ' h e Government of Provinces, as their Fee holden of the King, lome having greater, feme lefs Authority within their Territories: and, probably, all thofe were call d Barons that had fuch Seigniories or Lord- fh.ps, as are now call'd Court-Strom; who are the fame with Seigneurs in France. Soon after the Conqueft all luch came to Parliament, and fat as Peers in the Upper cl 5 ££ ST 1 -"?, ve, r y numerous, it was in the Reign ?i ,? g / ^"Ofdaind, that none but the Sarones majores fhould, for their extraordinary Wifdom, Intereft, or Qua- hty.be fummond to Parliament. But this State of the Nobility being very precarious, and depending folely on the Princes Plealure they at length obtain'd of the King Let- ters-Patent of this Dignity to them and their Heirs Male; Ml rftv aT C cM £*T n Vy,Patem > "Creation, whofl ihir ^nd F* I y Inhemance Lo "k of Parliament; of wh ch kind the King may create at his Pleafure. Never- thelefs there are Barons by Writ, as well as LetterT-Pa- tent; thole who were firft by Writ, may now iuft v be cM A Baron by Prefcriftion, for that they and the An- ceftors have continued Barons beyond the Memory of Ma" and by having their Simames annex'd to the Title of Lord; whereas Barons by latent are named by their Sa~ rome,. The Original of Barons by Writ, Calden refers to Henry III. and Barons by -Patent, or Creation, com- mencd in the time of Richard 11. To thefe there is a third kind added call'd Barons by Tenure, and fech are ■he Lords the B.fhops who, by virtue of Baromes ^eTi to their B.fhopricks fi, in the jj Houfe f p/ r ™ e ^f

and are call ct Lords Spiritual, formerly all Men were calld Barons, at leaf! all of the King's Family or that held immediately of him. Chamberlain offives, £« from the lime ot the Suppreffion of the Rebellion of the. Barons by Henry 111. only fuch among 'em as had conti nued loyal, were call'd by Writ to Parliament; and th t ttZth^ fP ttt « d f^ »/ thcRcalm,\ho were thus calld by Writ; and thus the others loft their Veerase Anuently the Earls -Palatine, and Earls Marches of &g-

land