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Show : — wi Ic is very well known, that Water has a very great Expanfion in Vapours 3 fo that évery cubick Inch of Water reduc d to Vapours, does exclude as much Air as the Quan- tity of Steam or Vapours it will produce s and, é@ contra, if thefe Vapours be exempt of included Air, the Condenfation of what ap- pertains to every cubick Inch of Water, leaves as great a Vacuum as the Difference is between theSpaces taken up by evaporated and natural Water. But is is evident that Vapours are empty, and their Expanfion is not made by Airinclos’d in the fmall Particles which confticute them, as is feen by thofe Engines that are contriv’d, by Raifing of Water by means of Steam. For the Condenfation of the Steam or Vapours caufes a Vacuum, which gives Room to the Preffure of the Atmofphere, to act as a Power for working the Machine; a Specimen of which we have in the Engine at Yorkin London. is it poflible upon the Principles of Nature, that have hitherto been difcover’d, that Vapours could afcend in the Medium of the Air, if their expanded Particles were filled by the fame Fluid: For, if fo, the That then he ftopp’d the Veffel by turning the Wire, andfeparating it from the Bellows, foundit weigh’d 24 Ounces 4; that is, it had loft 2 of an Ounce of its former Weight. The Content of the Bellows was 824,26 cubical Inches 5 but allowing for the Separ tion of the Boards, when compreffed, which were an Inch diftant, the Quantity of Va- pours therein, was but 745,75 cubical Inches ; fo that from 2 of an Ounce, or 1,42 cubical Inch of Water, filled 745,75 cubical Inches, without the Help of any Air. Befides, he repeated this Experiment, and when the Bellows were fill?d, he remov’d them from the Fire to a cool Place, where the Vapours condenfing, the Bellows was deprefsd by the Weight of the Atmofphere, ’till quite exhaufted, which could not have been, unlefs the Vapours were devoid of Air ; for otherwife that which they mutt have emptied would have fupported the Bellows. Wemay therefore, he fays, venture to conclude, that Vapours are made up offmalk excavated Globules of Water, which owe their Inflation only to Heat ; andthis feems to be confirm’d by their Abfolution of Cold. This is after the Rate of one Inch of Water to fill 2100,6 Inches of Steam or Va- Weight of the Water, together with that of pours, according to the fpecifick Weight of the included Air, would render each Particle or Veficula {pecifically heavier than Air of it felf, and then’ of confequence it muft fink, unlefs it were obftruéted by fome Caufe diff rent from that of Gravity. Therefore it is neceflary that Vapours be exhaufted, in order to their acquiring a Bulk that fhall render them Jighter than Air, in order to fwim therein. The faid ingenious Author, in order to prove that Vapours are not fill’d by Air, and the great Extent that Water occupies in Vapours, made ufe of the following Experiment. He caus’d a Bellows to be made of two cir- ‘Water. Some have afferted, that an Inch of Water makes 13000 Inches of Steam ; fo then, according to the Experiment before-mention’d, all the Waterthat falls in Rain, Snow, &c. poffeffed 2100,6, or to fay no more than 2000 times the Space, when it floated in the Atmofphere in Vapours, and the Condenfation thereof muft occafion Vacuums, which, ifcolleéted, would be a Space 2000 times greater than what is taken up by it in Water, which will put the furrounding Air in no {mall Mo- tion to reftore fo confiderable a Deficiency. _ It is not at all improbable, that there is cular Boards, of about ten Inches Diameter, which being filled, reprefenteda Cylinder 10 4 often affembled in the Atmofphere, a fuffici¢ Quantity of Vapours to maintain a lafting Condenfation, andthat it is alfo quick enough Inches in Height; over a Hole in the Centre at fometimes to create a great Wind. a of one of the Boards, he fixed a Pipe of one He adds, that according to Dr. Halley’s Experiment, it may be computed, that there is 129796,219 cubical Miles of the Atmofphere Inch and an half Diameter ; the End of this Pipe fhut into a Socket belonging to a Veffel, by which means there was a Communication between the Infide ofthe Bellows and of this Veffel, andthere was little Pin, which being turn’dround, ftopp’dthe Pipe, by a fmall Board that moved over it in the Infide of the Bellows : There was alfo a Wire in the fame manner, to ftop the Socket of the Veftel. Into this Veffel he poured a certain Quan- tity of boiling Water, which together with the Veffel weighed 25 Ounces 4 Troy-cweight, and then having comprefs’d the Bellows, and brought the two Boards clofe, he fix’d the Vefiel to it, binding fome Leather faft over the Part where they Joined, to prevent a Communication with the exterior Air. This Velfel being fet over the Fire, the Water con- tain’d in it was made to boil violently, the Steam of which immediately fwell’d the Beland quite filled it in a {mall Time. fill’d by Vapoursevery Day. This prodigious Quantity being divided andarrangedin clic: at various Situations throughout the W orld, occafions, by the mutual Condenfations, 2! moft conftant Refulrs of the Air, to fupply the empty Places, and he fuppofes, may thought abundantly fafficient for producing and maintaining all Winds univerfally. From thefe and other Confiderations he concludes, that the Pr tion of Wi ads depend chiefly on the Condenfation of Vapours 5 and in order to confirm his Hypothefis, proceeds to explain feveral Properties and Cates folvable thereby. ei a 1. That the Direétion or Courfe of Wind, is according to the Situation ot Body of Vapours, whofe Conde duces it; fo if a Conconrfe of gather’d over the Kingdom of France Condenfation thereof would draw the Air from, England in. a Southerly Direétion, in Spain would be a Northerly Wind, in Germany would blow Wefterly, at the Bay of Bifcay an Eafterly Wind. 2, That the Force or Intenfity of a Windis as the Extenfion ofthe condenfing Vapours, and the Quicknefs of their Condenfation, 3. He accounts for there being more Winds about the Equinoxes thanat other Seafons. 4. He adds, that it is underftood that the greater Quantities of Rain that fall in the Winter, muft occafion more Winds than in Sum- mer, there being a proportionable Quantity of Vapours condens’d ; andlikewife, 5. That there are more Winds in diftant ides than towards the Equator, becaufe former are more fubjeé&to Rain. 6. Why there is more Rain and Windin the Winter than in the Summer, when the Heat of the Sun in the former is more weak and languid, by whichit is incapable of raifing any great Quantity of Vapours to produce that Rain and Wind. 7. Why they have more Rain and Wind towards the Poles than about the Equator, altho’ the latter is a Part of the World where the Sun makes the greateft Evaporation. The Induftry of fome late Writers having brought the Theory and Produétion, and Mo- tion of the Winds, to fomewhat of a Mathematical Demonftration, we fhall here give it the Reader in that Form. Laws of the Produétion, 8c. of Winds. Ifthe Spring of the Air be weakened in any Place, more than in the adjoining Places, a Wind will blow throughthe Place where the Diminutionis. For, fince the Air endeavours by its elaftick Force to expand itlelf every Way, if that Force be lefs in one Place than another, the Nifus of the more againft the lefs elaftick, will be greater than the Mifus of the latter Lightnefs of the Atmofphere; therefore it is no Wonder if that foretels Storms. 4. Ifthe Air be fuddenly condens’din any Place, its Spring will be fuddenly diminith’d : Hence, if this Diminution be great enoughto affect the Barometer, there will a Windblow through the condens’d Air, _ §. But fince it cannot be fuddenly condenfed, unlefS it has before been muchrarefied 3 there will a Wind blow through the Air as it cools, after having been violently heated. 6. In like manner, if Air be fuddenly rarefied, its Spring is fuddenlyincreas’d ; where- fore it will flow through the contiguous Air, not acted on by the rarefying Force A Wind therefore will blow out of a Place in which the Air is fuddenly rarefied; and on this Principle it is, in all Probability, that, 7. Moft Caves are found to emit Wind, either moreor lef ——~ Since the Sun’s Power in rarefying the Air is notorious, it muft neceffarily have a great Influence on the Generation of Winds. The Rifing and Changing of the Wind is determin’d experimentally, by means of Wea= ter-cocks placed on the Tops of Houfes, € — But thefe only indicate what paffes about their own Height, or near the Surface of the Earth: /olfius affuring us, from Obfervations of feveral Years, that the higher Winds which drive the Clouds, are different from the lower ones, which movethe Weather-cocks. Mr. Derham obferves, upon compari veral Series of Obfervations made ofthe in divers Countries, viz. England, Ir zerland, ly, France, gland, Fc. That the Wisds in thofe feveral Places feldom agree; but when they do, it is commonly when they are ftrong, and of long Continu- ancein the fame Quarter; and more, he thinks, in the Northerly and Eafterly than in other Points —— Alfo, thata ftrong Wind in one Place is oftentimes a weak one in another; or moderate, according as the Places are nearer or more remote. againft the former —— The lefs elaftick Air, therefore, will refift with lefs Force than it is urged by the more elaftick; confequently the The Laws of the Force and Velocity of Wind. lefs elaftick will be driven out ofits Place, Windbeing only Air in Motion, and Aira Fluid, fubject to the Laws ofother Fluids, and the more elaftick will fucceed. If now the ExcefS of the Spring of the more elaftick, to that of the lefs elaftick, be fuch as to occafion a little Alteration in the Barofcope, the Motion both of the Air expell’d, and that which fucceeds it, will be- come fenfible. Q. E. D. 2. Hence, fince the Spring of the Air inereafes, as the compreffing Weight increafes, and comprefs’d Air is denfer than Air lels comprefs’d ; all Winds blow into a rarer Air out of a Place fill’d with a denfer. 3. Wherefore, fince a denfer Air is fpecifically heavier than a rarer, an extraordinary Lightnefs of the Air in be attended with Storms, any Place mutt extraordinary Winds or Nowan extraordinary Fall of the Mercury in the Barometer, ews an extraordinary its Force may be brought to a precile Computation : Thus The Ratio of the fp luid to that of Air Space that Fluid, impell’d by the A i we can determine the Space w b the of the 4 ted on by the fame Force, fame Time, by this R 1. As the fpecifick Gravity of Air is to that of any other Fluid, fo reciprocallyis the Square of the ace which that Fluid, im- pell’d by any Force, movesin any given Time, to the Square of the Space which the Air, by the fame Impulfe, will move in the fame Time. Suppofing therefore, the Ratio ofthe {peifick G ty of that other Fluid to that of : Air, |