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RARE, in Phyficks, a Body that is very, porous, whofe Parts are at great Diitance from one another, and which contains buc little Matter under a great deal of Built Sec Rarefaction* Body, Pore. In this Senfe Rare Hands oppofed to Denfe. See Density. The Corpufcular Philofophers, <viz. the Epicureans, Gajfendifis, Newtonians, &c. affert tiiat Bodies are rarer, fome than others, in virtue of a greater Quantity of Vacuity included between [heir Pores. The Carteftaus hold, that a greater rarity only con- fifts in a greater Quantity of Materia Sukilis, included in the Pores. Laftly, the Peripatetics contend, that Rarity is a new Quality fuperinduced upon a Body, without any Dependance, either on Vacuity, or fubtle Matter. See Cartesian, &c.
RAREFACTION, in Phyficks, the A&ion whereby a Body is render'd Rare ■ that is, whereby it comes to poffefs more room, or appear under a larger Bulk, without any Acceffion of new Matter. See Rare. Rarefaclion is oppofed to Condenfation. See Condensation. In firictnefs, however, our more accurate Writers reftrain.£tf- rtfdiiou to that Expanfion of a Mafs into a larger Bulk, which is t:ifecl:cd by Means of Heat; All Expanfion from other Caufes they call Dilatation. See Heat and Dilatation.
The Cartepans deny any fuch thing as ablolute Rarefatlion: Ex.'eajion, with them, conftituting the Effence of Matter, they are obliged to hold all Extenlion equally full. See Extension and Plenum.
Hence, they make Rarefatlion to be no other than an Ac- ceilion ot frefh, fubtle, and infenfible Matter, which entering the Parts of a Body, fenfibly diftends them. See this difproved under Vacuum.
Tis by RanfaEtion that Gunpowder has its effects; and to the fame Principle we owe our JEolipiles, Thermometers, ficc. See Gunpowder, Thermometer, ^Eolipile, <grt.
The Degree to which the Air is rarefyMe exceeds all Imagina- tion: Merfcnnus, long ago, by means of an intenfeHeat, found that Air might be rariivd, fo as to poffefs more than 70 times its former .Space.
Mr. Boyk afterwards found, that Air, by its own Elaflicity, and without the help of any Heat, would dilate is felf fo as to take up 9 times its former Space; then 3 1 times; then 60; then 150; at length, by many Degrees he found it would reach to 8000 rimes, then iqooo, then 13679- Sec Elasticity.
Such is the Rarefaction of common Air, from its own Prin- ciple of Elailicity, and without any previous Condenfation; but if it be comprefs'd, the fame Author found its greatefb Space when moft. rarified, is to its leaft when moil condens'd, as 750000 to 1. See Compression.
Such an immenk Rarefaclio?t, Sit IJaacNeivton (hews, is incon- ceivable on any other Principle than that of a repelling Force inhe- rent therein, whereby its Particles mutually fly from one another. See Attraction, &c.
This repelling Force he obferves is much more confiderable in Air than in other Bodies, as being generated from the raoft fix'd Bodies, and that with much Difficulty, and fcarce without Fermentation : Thofe Particles being always found to fly each other with the moft Force, which when in Contact, cohere the moft firmly. See Repelling-Po-uw.
The Members of the French Royal Acadamy have beftowed a world of Attention on the different RarefaSiims, or rather the different Rarities of the Air at different Heights. M. Ma- rime eftablifhed this as a Principle, from Experiments, that the different Rarefactions or Condcnfations of the Air follow the Proportion of the Weights wherewith 'tisprefs'd.
Hence, fuppofing the Mercury in the level of the Sea fuf- pended to 28 Inches, which is the Weight of the whole At- tnofphere; and that 60 Foot Height of Air are equivalent to a Line, or T ' r of an Inch of Mercury; fo that the Barometer at the Height of 60 Foot from the Sea, would fall a Line; 'tis eafy finding what Height of Air would be equal to a Second, or any other Line of Mercury: For as 28 Inches of Mercury, ?'» are to 28 Inches, fo is the Height of 60 Foot of Air, to a fourth Term; which is the Height of Air correiponding to a fecond Line of Mercury.
And after the fame manner may the Heights of Air corre- fponding to each Line be found; which will make a Geometri- cal ProgrclTion. the Sum whereof will be the whole Height of the Atmofphere. Of" confequence a certain Part of that Sum w ill be the Height of a Mountain; at whofe Top the Barometer ftiall have funk a certain Quantity. See Mountain.
MefT Cajfini and Maraldi, upon meafuring the Heights of fe- deral Mountains, found that thisProgreffionof M.Mariotte, was defective ■ that it always gave the Height of the Mountains, and corireq Uer ] t iy rhe Rarefaclions, lefs than they really were; and • r °m ibme new Experiments M. Amontons found that the Prin- °pfe will only hold in the mean Rarefactions, not in the Ex- tremes. See Air.
^AREFACTIVES, or Rarefacientia, in Medicine, Re- medies which open and enlarge the Pores of the Skin, to give an eafyV entt0 the M atter of Perfpiration. See Perspira- tion.
Such are Anife, Mallows, Pellitory. Camomile-Flowers, Line- Seed, &(, '
RASANT, in Fortification. Rafant Flank, or Ling, is that Part of the Curtain, or Flank, whence the Shot exploded raze or ff" aioi, g the Face of the oppofue Baftion. Sec Flank.
The Defence of the Baftion is Rafant. See Defence.
RASH, in Medicine, anErruption or Efflorefcence upon the Skin, thrown out in Fevers or Surfeits. See Surfeit, eh-c
RASP, a fort of File. See File.
RASPHUYS, or Rasp-Hw/?, a celebrated Work-houfe or Houfe of Correction, at Amsterdam. See Work-Hw/5.
RASPATORY, a Chirurgeons Inftruments wherewith they fcrape foul, carious, or fracf tired Bones.
RASURE, Rasement. See Erasure.
RATAFIA, a fine fpirituous Liquor, prepared from the Ker- nels, &c. of feveral Kinds of Fruits, particularly Cherries and Apricocks.
Ratafia of Cherries is prepared by bruifing the Cherries, and putting them into a Veflel wherein Brandy has been kept; then adding to them the Kernels of the Cherries, with Strawberries, Sugar, Cinnamon, white Pepper, Nutmegs, Cloves; and t6 20 Pound of Cherries, 10 Quarts of Brandy.
The Veflel is left open 10 or 12 Days, then ftopp'd clofe, for two Months e're it be tapp'd.
Ratafia of Apricocks is prepared two ways; viz. either by boiling the Apricocks in white Wine, adding to the Liquor an equal Quantity of Brandy, with Sugar, Cinnamon, Mace, and the Kernels of the Apricocks; infufing the whole for 8 or 10 Days; then ftraining the Liquor, and putting it up for Ufe: Or, by infuiing the Apricocks, cut in Pieces, in Brandv, for a Day or two; palling it through a ftraining Bag, and putting in the ufuat Ingredients.
RATCH, in Clock- Work, a fort of Wheel, which ferves to lift up the Detents every Hour, and to make the Clock ftrike. See Clock.
RATCHETS, in a Watch, are the fmall Teeth at the Bot- tom of the Barrel, which flop it in winding up. See Watch.
RATE, a Standard, or Proportion by which the Quantity or Value of a thing is adjufted. See Standard.
The Rates of Brcad_, &e. in London, are fix'd by Authority. See Assise.
The Rate of Intereft, as now eftablifhed by Law in England, is 4 per Cent. The Rate of Intereft in Italy is 3 per Cent. In Sweden 6. In France 7. In Spain 10. laScotland 10. InBar- badoes 10. In Ireland 12. In Turky 20. See Interest.
Low Rates of Intereft advance the Prices of Land.
The Rates or Fares of Hackney-Coachmen, ChairmeD, and! Watermen, are fix'd by Act of Parliament, 14 Car. II, See Hackney-Coach, &c.
The Rates of Exchange, Factorfhip, drc. are different. See Exchange, Factorage, &c.
RATZ-Tythe. When Sheep, or other Cattle, are kept in a Pa- rifh for lefs time than a Year; the Owner muff, pay Tythe for them, pro rato, according to the Cuftom of the Place. See Tythe.
Rate, of a Ship of War, is its Order, Degree, or Diitindi- on, as to Magnitude, Burthen, &c. See Ship, <&c
The Rate is ufually accounted by the Length and Breadth of the Gun-Deck, the Number of Tuns, and theNumberof Men and Guns the Veffel carries.
A Firfi Rate Man of War has its Gun-Deck from 159 to 174 Feet in Length, and from 44 to 50 Foot Broad; contains from 13x3, to 1882 Tuns; has from 706 to 800 Men; and carries from 96 to no Guns. See Navy.
Second Rate Ships have their Gun-Decks from 153 to i6< Foot long; and from 41 to 46 broad; they contain from 1086 to 1482 Tuns; and carry from 524 to 640 Men; and from 84 to 90 Guns.
Third Rates have their Gun-Decks from 142 to 158 Foot in Length; from 37 to 42 Foot broad; they contain from 871 to 1262 Tuns; carry from 589 to 476 Men; and from 64 to 80 Guns.
Fourth Rates are in Length on the Gun-Deck, from 118 to 146 Foot; and from 29 to 38 broad; they contain from 448 to 915 Tuns; carry from 226 to 346 Men; and from 48 to 60 Guns.
Fifth Rates have their Gun-Decks from 100 to 120 Foot long; and from 29 to 3 1 broad; they contain from 259 to 542 Tuns; carry from 145 to 190 Men; and from 26 to 44 Guns.
Sixth Rates have their Gun-Decks from 87 to 95 Foot long; and from 22 to 25 Foot broad; they contain from 152 to 256 Tuns; carry from 50 to no Men; and from 16 to 24 Guns.
Note, The new-built Ships arc much larger, as well as better than the old ones of the fame Rate; whence the double Num- bers all along; the larger of which exprefs the Proportions of the new-built Ships, as the lefs thofe of the old ones.
For the Number of Veffels of each Rate in the Englifj Fleet, fee Navy.
RATEEN, or Ratine, in Commerce, a thick woollen Stuffj crofs'd; wove on a Loom with four Treddlcs, like Serges and other Stuffs that have the CrofEng.
There are fome Ratines dr efsM and prepar'd like Cloths; o- thers left {imply in the Hair; and others where the Hair or Nap is frized. r-
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