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«nd tenacity of foftened rofin ; then it is rolled into the 

 form of a ball, generally kept tied up in a rag, and when 

 it is ufed, infufed into water, till it ^ives fome colour to 

 that liquid. Mac. Chcin. Diet. Eng. Ed. 



Balls, Mcrcurid!, an amalgam of merciiiy and tin fuf- 

 ficiently folid to be moulded, and to prefen-e'a folid form. 



To make mercurial balls, add mercury- to its weight of 

 melted tin, and pour the fluid mafs into a round and hollow 

 mould. 



Thefe balls have been employed to purify water in which 

 they are boiled, an opinion whicli is perhaps in fjme de- 

 gree well-founded, fince mercury even in imperceptible quan- 

 tity id known to deftroy animalcula:. However, the boiling 

 alone would probably product nearly the fame effcA, and 

 the mercurial balls are no longer in ufe. The tin is not an 

 ufelefs addition, lince befides giving the mafs a proper con- 

 fiftence, it aflifts moft materially in the oxydation, and there- 

 fore the folubility, of the mercury. 



Balls, in Elcciridly, are two pieces of cork, or pith of 

 elder, nicely turned in a lathe, to the fize of a fmali pea, 

 and fufpended by fine linen threads ; intended by Mr. Can- 

 ton as eleftrometers, and of excellent ufe to difcover fmall 

 degrees of electricity, to obferve the changes of it from 

 pofitive to negative, and vice verfd ; and to eilimate the 

 force of a (hock before the difcharge, fo that the operator 

 fhall always be able to tell very nearly before the difcharge, 

 by knowing how high he has charged his jars, what the ex- 

 plollon will be. 



Balls, CryJlc.Uhte, m Natitra! Hiflory. There are two 

 forts of foffile bodies mentioned in authors by this name, 

 and diftinguifhed into the tchinated and concave. The Hrlt 

 are roundilb nodules of ftrong matter, covered over with 

 points of cryllal ; and the other, flints and other ftones, 

 having cavities in their middles, which are lined, or crulled 

 over with thefe cryftals. 



Ball, Vegetalle, a very particular kind of plant of a 

 deep green colour, of an irregularly fpheric.'il (hape, hollow 

 within, and of different fizes, from an inch and a half to 

 three inches in diameter. It probably belongs to the Con- 

 ferva genus, in the clafs of molfes ; though Mr. Ray has 

 ranged a fimilar plant under the genus of Alcvonium. 

 (See Coral.) Phil. Tranf. vol. xlvii. art. 83. an. 1752. 



Ball, Puff. See Lycoperdon. 



Ball, Hero's, Pila Heroii'is, in Hydraulics, is a kind of 

 artificial fountain, wherein the water is made to fpout from a 

 hollow ball or globe. 



It takes the denomination from the inventor, Hero of 

 Alexandria, who has left the dcfcription of it in his Spi- 

 ritalia. See Fountain. 



Balls of Fire in the air, in Meteorology, are meteors 

 fometimes feen paffiiig over countries, and computed by phi- 

 lofophers to be at a veiT confiderable height in the atmo- 

 fphere. They fometimes burll at that height ; and though 

 the air mutl be exceeding rare there, yet the explofion is 

 heard at that diftance, and for feventy miles round on the 

 furface of tlie earth, &c. Does not this look as if a rare 

 atmofphere, almoft a vacuum, was no bad conduflor ot 

 found I Dr. Franklin's Works, p. 437. 



Among the phenomena of the atmofphere, the large me- 

 teors called fire-balls, and bolicles, have in modern times ex- 

 cited particular attention. Mr. C. F. Fulda has coUefted a 

 variety of obfei-vations refpefting thefe phenomena, in a pa- 

 per read to the Phyfical Society of Gottingen, Dec. 7, 

 1796, and publiflied in profelTor Gmelin's " Gottingifches 

 Journal der Naturwinenfchafften, voLi. part 1. Tiicfe me- 

 teors, he obferves, appear in evcrj- climate in fouthern aud 



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northern latitude, as well as under the equator. Ther arr 

 alfo feen at every feafon of the year, and at every «'eri'id'r i 

 the day, and for the moll part wlicn the flcy is fcrcDe, fome 

 ot them proccediiig from light clouds, whicti has gjven ot- 

 cafion for fuppofing tliat they originated at a greater height 

 than thefe clouds ; and they have been obfervtd to move 

 with diflerent degrees of rapidity, fome proceeding at about 

 1530 feet in a fecond or even with a flower motion, and 

 others moving at the rate of thirty Englifh milci in the fame 

 time, or with a velocity greater by 3! miles in a fecond 

 than that of the earth in its orbit. They proceed from, a« 

 well as towards, all jioints of the compafs : however, moil 

 of them have appeared in the northern or fouthern parts of 

 the horizon ; and yet no general conclufion, in refpcft of 

 their connection with the northern or foutlicrn lights, can 

 be deduced from this circumftancc, though fome obfcrvation* 

 made in Sweden feem to favour fuch an hypothtfis. Ther 

 do not always move according to the diredtion of the windi 

 nor is their velocity proportioned to that of the wind. 

 When, indeed, they have appeared, it has gencrallv been 

 calm ; but fome of them have been fucceeded bv eveti 3 vio- 

 lent wind. They alniolt all defcend towards the earth, aiid 

 from a rarer to a denier atmofphere, as mav be inferred 

 from their foon becoming confiderablv enlarged. Some, 

 however, have proceeded in an horizontal direction over the 

 furface of the earth, but none of them appear to move up- 

 wards. Their form is fometimes perfectly globular, and 

 fometimes more fpindle-lhaped, fo that their length has occu- 

 pied feven or eight degrees of the heavens. When they 

 move witli a great velocity, they have been followed by a 

 long tail, which has been afcribed to the continuance of the 

 imprelHon male on the eye. Others, tiiat have moved flow> 

 Iv, appeared as if the tail, or part of it, belonged to the 

 body itfelf ; and it (liould feem that the long train, which 

 marks their courfe, ought often to be accounted for by 

 traces left behind them i-ather than by mere imprcffion. 

 Their apparent magnitude has been ver)' different ; but fre- 

 quently larger than that of the moon. Few of them have 

 hnd an apparent motion round their axes. Moll of them 

 diffufed a very lively dazzhng light ; but the fmaller num- 

 ber have exhibited a faint light ; their colour and I'plendor 

 have been very difftrent and variable, fometimes red, fome- 

 times blue, fometimes violet, fometimes in part yellow or 

 da/.zliug white, and fometimes exhibiting the prifmatic co- 

 lours. Sonic have been feen to burn with a bright flame, 

 and others as if in a Hate of ignition. Their real diameter, 

 afcertained by aiftual meafurement or by conjecture, has been 

 aUvavs very confiderable. The diameter of that concerning 

 which fir John Pringle made calculations from various ob- 

 fervations which he collected (Phil. Tranf vol. LI. pt. I. 

 p. 218.), and that of the meteor feen by Mr. Rittenhoufe 

 at Phil.idelphia, in October 17-9 (Anieric. Tranf. vol. ii. 

 p. 175.), were at moll about half a German mile. Thefe me- 

 teors fe»-m to originate at a very differer.t, but moll of them 

 at a very confiderable, htiglit above the furlace of the 

 earth. All of them, whofe mean or greatcll height has 

 been the fubjcc\ of calculation, were elevated above the 

 higlieil clouds, as clouds are fcarcely perceptible at the 

 height of I 3,500 toifes ; and Sllherlchlag found the greateft 

 height of the fire-ball, which appealed in July 1762, to be 

 72,276 toifes. On this account their origin, as Reiniarus 

 anil Ciiladni have fiippofed, is not to be alcnbed merely to 

 electricity ; but others have conliilered them as produced 

 by the acti«n of the electric fluid between the clouds and 

 the nortiiern lights ; and this hypothclis fufficiently corre- 

 fponds to their actual height, hecaule by the meafurement 

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