A E R 



tTie experience of manners, partly from ndrological confi- 

 deratioiis ; i iide. t e titk" of a erom anti A. 



tEROMKLI, a name givLii to honey, and alfo to 



MANNA. Sie Dro OMEI.I. 



AF.ROMETRY, Akromf.tria, compounded of xr,f, 

 air, and //STpiiv, to meafure, tlie art of meafuring the air, its 

 poweis, and properties ; and inchiding the laws of the mo- 

 tion, gravitation, prcfi'ure, elafticify, reliaftion,condenfation, 

 &c. oi the atmofpherical fluid. 



The word aeromotry is but little ufed : in lieu hereof, 

 we commonly call this branch of philofophy, pneumatics. 

 C. Wolfius, profeffor of mathematics at Hall, having re- 

 duced many of the affeAions of this fluid to geom.ctrical 

 demonftration, fiift publilhed Elements of Aerometry, at 

 Leipfic, 1709, in high Dutch, and a! towards more largely 

 in Latin, which have been t\vice inferted in his Ciirfus Malhe- 

 matitriis, in eight volumes 410. 



AERONAUTICA, from aiip, and vaurixo?, derived from 

 va.-j^,Jhij>, the art of failing a vefTel through the air, or atmof- 

 phere, iullained as a (liip in the fea. 



AEROPHOBIA, formed of anp, air, and (^0^0:, fear, a 

 term that has been fometimes ufed for the dread of frefh air. 

 Dr. Franklin fays, that he has been fometimes feizcd with 

 this aerophobia, confidering frelh air as an enemy, and ex- 

 cluding it from the rooms which he has occupied. But 

 experience convinced him of his error, and taught him to 

 regard frefli air as eminently conducive to health. Any air, 

 he fays, is preferable to that of a clofe chamber, whicii has 

 been again and again refpired without any change. The 

 fame fagacious philolopher has occafionally rallied thofe vale- 

 tudinarians, who, wrapping thcmfelves in clofe gamients, 

 hurr)- from the noxious air of a clofe chamber with as much 

 of it as they can carry with them into as clofe a carriage, 

 from which the external air is carefully excluded, and thus 

 proceed to take the air for the benefit of their health. 



AEROPHYLACEA, in Natm-al Hijlary, denote fub- 

 terraneous receptacles of air or wind. 



The word is compounded of anp, air, and iffAaini, cii/Irjdia, 

 ietping. — In which fenfe aerophylacea ftands contradiftin- 

 guifhed from hyilrophyLicea, pyrophylacea, &c. 



Kircher ipeaks much of aerophylacea, or huge caverns, 

 replete with air, diipofed under ground, from whence, 

 through numerous occult palfages, that element is conveyed 

 either to fubterraneous receptacles of water, which are 

 hereby raifcd into fprings or rivers, or into the funds of fub- 

 terraneous fire, which are thus fed and kept ahvc for the 

 reparation of metah, minerals, and the like. 



jEROPUS, in Entomology, a fpecies of Papilio, having 

 brown wings marked with a yellow band and a fmgle ocellus 

 at the bafe of the primores. It is found in India and 

 South America. 



^Ropus, in Ancient Geography, a mountain of Mace- 

 donia. 



AEROSIS, among the Ancient Phyficians, denotes the 

 aft whereby the blood is attenuated and converted into an 

 aura for the fupport of the vital fpirits, and the mainte- 

 nance of the flame of life. 



AERO.STATICA, from anf, and ra-rixo;, from 'iTifji, 

 JlniW), is ufed by iorae authors for the fcience called by others 

 AERoMF.TRY. It is properly the doi!:trine of the weight, 

 prefTnrf and balance of the air and .\tmosphere. 



AEROSTATION, formed of atjj, air, and r^/mi, of 

 •rn^i, / 'weigh, the fcience of lueights, in its primary and 

 proper fenfe, denotes the fcience of weights, fufpended 

 in the air ; but in the modern application of the term, it 

 fignities the art of navigation through the air, both in the 

 principles and the praflice of it. Hence alfo the macliines. 



A E R 



whiclt are employed for this puq>ofe, arc called arrof.ats, or 

 aerojiatic machines ; and, on account of their round figure, 

 air-balloons. The aeronaut, formed of xnf and mw:, jailor, 

 is the perfon who navigates though the air by means of 

 fuch machines. 



Afrostation, principles of. The fchdamental princi- 

 ples of this art have been long and generally known ; 

 although the apphcation of them to prattice feems to be 

 altogether a modern difcovcry. They are particularly 

 illuftrated in this Diftionaiy under the articles IVeight of 

 Air, Elaflicity of Ais., and Specific Gravity. 



It will be fuiiicient, therefore, to obferve in thir. place, 

 that any body, which is fptcifically, or bulk for hulk, 

 lighter than the atmofpheric air encompalfing the earth, will 

 be buoyed up by it, and afcend ; but as the deniity of the 

 ATMOSPHERE decrcafcs, on account of the diminilhed prcf- 

 fure of the fuperincumbent air, and the elaftic property 

 which it poflTcfTes, at difierent elevations above the earth, this 

 body can rife only to a height in which the furrounding 

 air will be of the iamc fpecific gravity with itfelf. In this 

 fituation it will cither float, or be driven in the direftion of 

 the wind or current of air, to which it is expofcd. An 

 air-balloon is a body of this kind, the whole mafs of which, 

 including its covering and contents, and the feveral weights 

 annexed to it, is r,[ lefs fpecitrc gravity than that of the 

 air in which it rifes. 



Heat is well known to rarefy and expand, and confe- 

 quentJy to leflen the fpecific gravity of the air to which it 

 is applied ; and the diminution of its weight is proportional 

 to the heat. To the obfervations that occur under Jilaf- 

 ticity of A IK to this purpofe, we fliall here add, that one 

 degree of heat, according to the fcale of Fahrenheit's 

 thcnuometer, feems to expand the air about one four hun- 

 dredth part; and about 400, or rather 43 j, degrees of 

 heat, will juft double the bulk of a quantity of air. If, 

 therefore, the air inelofed in any kind of covering be heated, 

 and confequently dilated, to fuch a degree, as that the ex- 

 cels of the weight of an equal bulk of common air above 

 the weight of the heated air, is greater than the weight of 

 the covering and its appendages, this wliole mafs will afcend 

 in the atmofphere, till, by the cooling and condenfation of 

 the included air, or the diminilhed denfity of the furround- 

 ing air, it becomes of the fame fpecific gravity with the air 

 in which it floats ; and without renewed heat, it will gra- 

 dually dcfcend. 



If, inftead of heating common air inelofed in any cover, 

 ing, and thus diminilhing its weight, the covering be filled 

 with an elafl.ic fluid, lighter than atmofpheric air ; fo that 

 the excefs of the weight of an equal bulk of the latter 

 above that of the inelofed elaftic fluid be greater than the 

 weight of the covering and its appendages, the whole mafs 

 will in this cafe afcend in the atmofphere, and continue to 

 rife till it attains a height at which the furrounding air is of 

 the fame fpecific gravity with itfelf. Inflammable air is a 

 fluid of this kind. For the knowledge of many of its pro- 

 perties, we are indebted to Mr. Henry Cavendifli ; who 

 difcovered, that if common air is eight hundred times 

 lighter than water, inflammable air is feven times lighter 

 than common air ; but if conunon air is eight hundred and 

 fifty times hghter than water, then inflammable air is 10,8 

 times lighter than common air. See Phil. Tranf. vol. Ivi. 

 art. 19. and Inflammalle A\k or Hydrogen. 



The conftruction of air-balloons depends upon the prin- 

 ciples above fl:ated ; and they are of two kinds, as one 

 or the other of the preceding methods of preparing them ig 

 adopted. 



Aerostation, hiftory of. In the various fchemes that 

 Pp 2 have 



