R A R 



RAPPO Rai'PO, a bay on the coafl of Mowce, one of 



the Sandwicli iflands. 



RAPPOLTSKIRCHEN, a town of Auftria; five 

 miles S. of Tiihi. 



RAPPORT, Fr. in Miijic, is foinetiincs ufetl for propor- 

 tion, and foinetimcs for relation, words wliich will be ex- 

 plained in their places. 



RAPPS, in G'Sography, a town of Auftria, on the river 

 Taya ; four miles S. W. of Drofendorf. 



RAPSO, a town of litria ; 52 miles S.E. of Capo 

 d'Iftria. 



RAPTEC, a river of HinJoortan, which runs into the 

 Dewah, five miles S.VV. of S-lkmpour. 



RAPTU H^KEDIS, in Law, an ancient writ which lies 

 for taking away an heir, holding" in focage ; of which there 

 are two forts ; one when the heir is married, the other when 

 not. See Ravishment. 



RAPTURE, Raptuua, an cxtafy, or tranfport of 

 mind. .See ExTASY, Enthusiasm, Rhapsody, &c. 



RAPUNCULUS, in Botany, the Rampioii, owes its 

 name to a reiemblancc in the root to a Rape, or oblong 

 Turnip. This root, Campanula Rapunculus of L'-unxus, is 

 biennial, fcarcely larger than a radiih, vs'hich it refembles 

 alio in fhape, but the colour is white. Its flavour is iweet 

 and mild, notwithftanding fome degree of inilkiueis in the 

 juices, in which it accords with other, ufually bitter and 

 acrid, fpecies of its genus. The Rampion is now mubh lefs 

 cultivated than formerly, and almolt a itranger at our 

 tables. 



RAPUNTIUM, a name ufed by Tournefort and Mori- 

 fon for fome plants referred to Lobelia by Linnajus. See 

 L.OBELIA. ) Gartner, having adopted Plumier's Lobelia, the 

 Linnasan Scisvala, reftores Rapuntium ; but fuch a meafure 

 could now lead to inconvenience only. 



RAPLITIA, fo called by Aublet, becaufe the plant 

 grows in the iorells of Orapu in Guiana. Jufiieu and La- 

 marck have retained this curious name. Schreber has 

 changed it for SciuRls ; fee that article hereafter. 



RARAKIT, in Geography, a town of the ifland of 

 Ceram, at the foot of a mountain covered with trees, which 

 ferves as a harbour for pirates. 



RARE, in Phyjir.s, denotes a body that is very porous, 

 whofe parts are at a great diftance from one another, and 

 which contains but little matter under a great deal of bulk. 



In this fenfe rare Hands oppofed to dtnfe. 



The corpufcular philofophers, i'i=. the Epicureans, Gaf- 

 fendiits, Newtonians, &c. aflert that bodies are rarer fome 

 than others, in virtue of a greater quantity of vacuity in- 

 cluded between their pores. The Cartefians hold, that a 

 greater rarity only confifts in a greater quantity of materia 

 fubtilis included in the pores. Laftly, the Peripatetics 

 contend, that rarity is a new quality fuperinduced upon a 

 body without any dependence, either on vacuity, or iubtile 

 matter. 



RARECOURT, in Geography, a town of France, in the 

 department of the Meuie ; lo miles S.W. of Verdun. 



RAREE, a town of Hindooftan, in Concan ; zo miles 

 N.N.W. of Goa. — AU'o, a town of Hindooftan, in Bahar ; 

 II mile's N.N.W. of Durbungah. 



RAREFACTION, Rarefactio, in W-v/z^j-, the atl by 

 which a body is rendered rare; that is, is brought to poH'efs 

 more room, or appear under a larger bulk, without ac- 

 ceffion of any new matter. 



Rarefa3hn is oppofed to comlaij'alion. 



Our more accurate writers reftrain rarefaftion to that 

 expanfion of a mafs into a larger bulk, which is cffedled by 



R A R 



means of heat. All expanfion from other caufes they call 



dilatatujtt. 



The Cartefians deny any fuch thing as, abfolute rare- 

 faftion : cxtenfion, with them, coiiftituting the efl'ence of 

 matter, they are obliged to hold all extenfion equally full. 



Hence, they make rarefadtion to be no other than an ac- 

 ceffion of fredi, fubtilt, and infenfible matter, which, enter- 

 ing the parts of the body, fenfibly diftends them. See this 

 difproved under Vacuum. 



It is by rarefadion that gunpowder has its effc-ft ; and 

 to the fame principle alfo we owe our asohpilcs, thermo- 

 meters, &c. 



The degree to which the air is rarefiable exceeds all ima- 

 gination : Merleunus, long ago, by means of an intenfe 

 heat, found that air might be rarefied fo as to poflefs more 

 than feventy times its former fpacc. 



Mr. Pioyle afterwards found, tiiat air, by its own elafticity, 

 and without the help of any heat, would dilate itfelf fo as 

 to take up nine times its former fpace ; tlien 31 times; 

 then 60 ; then i 50 : at length, by many degrees, he found 

 it would reach tu 8000 times, then 10,000, and finally to 

 I3.,679. 



Such is the rarefaftion of common air, from its own 

 principle of elafticicity, and without any previous condenfa- 

 tion ; but if it be comprelled, the fame author found its 

 greateft fpace when moit rarefied, is to its leaft when moft 

 condenfed, as 55,000 to i. 



Such an immenfe rarefaftion, ur Ifaac Newton Ihews, 

 is inconceiveable on any other principle than that of a 

 repelling force inherent in the air, by which its particles 

 mutually fly from one another. 



This repelling force, he obferves, is much more confider- 

 able in air than in other bodies, as U,eing generated from 

 the moft fixt bodies, and that with much difficulty, and 

 fcarcely without fermentation ; thofe particles being always 

 found to fly from each other with the molt force, which, 

 when in contaft, cohere the moft firmly. See Air. 



The members of the French Royal Academy have be- 

 llowed mucii attention on the different rarefadtions, or rather 

 the different rarities of the air at different heights. M. 

 Mariotte eftabliflied this as a principle, from experiments, 

 that the different rarefaflions, or condenfations, of the air, 

 follow the proportion of the weights with which it is 

 preffed. 



Hence, fuppofing the mercury in the level of the fea 

 fufpended to twenty-eight inches, which is the weio-ht of 

 the whole atmofphere ; and that fixty feet height of air 

 are equivalent to a line, or one-twelfth of an inch of mer- 

 cury ; fo that the barometer, at the height of fixty feet 

 from the fea, would fall a line ; it is eafy finding what 

 height of air would be equal to a fecond, or any other line 

 of mercury : for as twenty-eight inches of mercury one- 

 tweifth are to twenty-eight inches, fo is the height of fixty 

 feet of air to a fourth term, which is the height of air cor- 

 rcfponding to a fecond line of mercury. 



And after the fame manner may the height of air cor- 

 refpoiiding to each line be found ; which vi'ill make a geo- 

 metrical progrefiion, the fum of which will be the whole 

 height of the Atmosphere (which fee) ; and, of confe- 

 quence, a certain part of that fum will be the height of a 

 mountain, at whofe top the barometer (hall have funk a 

 certain quantity. 



Mefl'rs. Caflini and Maraldi, upon meafuring the heights 

 of leveral mountains, found, that this progrefiion of M. 

 Mariotte was dcfefrtive ; that it always j;ave the height of 

 the mountains, and confequently the rarefactions, lefs than 

 they really were ; and from fome farther experiments, 



M. Amon- 



