B A L 



upper arm, another arm i| inch long, projec'\s from the pillar 

 at ri^^ht angles, with a hole through it two lines long, and a 

 quarter of a line broad, and placed perpendicularly below 

 the piiUey of the upper arm, to receive a fmall plate' 1 1 inch 

 loig, and of fuch breadth and ihickncfs that it may frcily 

 move up and down, and yet not play too freely in the hole. 

 At each extremity of the plate is a finall hook. The whole 

 of this apparatus is enclofcd in a fmall cafe (Jig. 13.), fur- 

 nilhed with glaffes, a, a, a, at the top and about it. The 

 manner of uling the alTay-balance is to pafs a filken ftring 

 over the three pulHes of the fnpport and arm ; then the fup- 

 port is placed in the middle of the fmall cafe, and the other 

 end of the filk ftiing is paffed below through a hole in the 

 middle of the lower part of the frame, containing the win- 

 do a- in the fore part of the cafe, and fattened to a fmall 

 Weight of a cubic form. The fork of the balance is fuf- 

 pended on the inferior hook of the plate. By moving 

 backwards and forwards the weight fattened to the ftring, 

 placed upon the top of the drawer projefting beyond the 

 fore-part of the cafe, the balance within is either raifed or 

 lowered. The bodies to be weighed, and the weights 

 themfelves, being put into the dilhes ; the ditties are put 

 into the fcales, through the fide windows, which mutt be 

 opened for that purpole. When any thing is added or 

 taken away, by means cither of the pincers, or of the fmall 

 (hovel, or fpoon, the balance is let down that the fcales 

 raay rett upon the bottom of the cafe ; and before it is lift- 

 ed up again the windows mutt be ttiut, efpecially if the air 

 is not peifedly ftill. The flat pieces of glafs, often placed 

 under the fcales of an attay-balance, feem, by their eleftri- 

 cal power, capable of attrafting, and of thus caufing the 

 lighter fcale to preponderate where the whole matter weigh- 

 ed is fo very fmall. See Phil. Tranf. N"^ 480. p. 245. 

 The eleftricity of a flat furface about three inches fquare 

 has been known to hold down one f.ale, when there was 

 a weight of about 200 grains in the other. 

 Balance, in Afironomy. See Libra. 

 . Balance, in Horology, is that part of a clock or watch, 

 which by its motion regulates and determines the beats. — 

 The circular part of it is called the r'nn, and its fpindle the 

 verge ; there belong to it alfo two pallets or nuts, which 

 play in the fangs of the crown-wheel ; in pocket watches, 

 that ftrong ttud, in which the lower pivot of the verge 

 plays, and in the middle of which one pivot of the crown- 

 wheel runs, is called \\\e. p'jtcuce : the wrought piece which 

 covers the balance, and in which the upper pivot of llic ba- 

 lance plays, is the cock : tlie fmall fpring in the new pocket- 

 watches is called the RfCULATOR. 



It appears from the tettimony of hittorical accounts, as 

 well as other evidences, that the balance was univerfally 

 adopted in the conttruftion of the lirft clocks and watches ; 

 nor was it till the year 1657, that Mr. Huygens united pen- 

 dulums with clock-work. (See Pendulum.) In watches 

 of early conttrilclion, the balance vibrated merely by the 

 impulfes of the wheels, without any other control or regula- 

 tion ; the motion communicated to the balance by one 

 impulfe continued till it was deftroyed, partly by fric- 

 tion, and partly by a fucceeding impulfe in the oppofite di- 

 rcftion ; and therefore the vibrations mull, of courfe, have 

 been very unlleady and irregular. Thefc imperfeAions were 

 in a great meafure remedied by Dr. Hooke's ingenious in- 

 vention of applying a fpiral fpring to the balance, the adlion 

 of which on the balance of a watch is ttmilar to that of gra- 

 vity on a pendulum ; each kind of force having the elfed 

 of correfting the irregularities of impulfe and refillance 

 which otherwife ditturb the ifochronifm of the vibrations. 

 In clocks and watches, the real meafure of time is the ba- 

 Vol. in. 



B A L 



lance, and all the other work fcnes merely to continue tl<« 

 motion of the balance, and to indicate the time as mcafurtd 

 by its vibrations. The regularity of a timc-ktepcr will 

 therefore depend on that of the time in which the balance 

 vibrates ; and the invcttigation of this time of vibration, 

 from the fevei-al data or conditions on which it depends, is 

 an important objefl in this part of mechanical fcicnce. See 

 Escapement, Clock, Time-keepers, and Watchis. 



That the balances of watches, when m.annfacturcd of 

 fteel, as they generally are, might be in a fmall degree mag- 

 netic, and that this property might have fome influence in 

 difturbing their vibrations, fome have fiifptfted, and others 

 have denied; but Mr. Varley has lately (fee Philof. Majaz. 

 vol.i. p.iH.) pointed out a fource of error which has been hi- 

 therto little, if at all, apprehended ; and thij is the polarity 

 of the balance, or tendency of a particular point to tlic north ; 

 ard of an oppofite point to the fouth, fo IWong as to be 

 fufficient materially to alter the rate of going of the machine, 

 when put in different pofuioiis. If this caiife of ciTor had 

 been known, the ufe of fteel balance? would have been laid 

 afide long ago, particularly where accurate perforniarxc is 

 indifpenfable, as in time-pieces for aftronomical ar.d nautical 

 purpofes. Mr. X'arley, having afcertained the facl, and 

 knowing the pofition of the poles, proceeded to examine 

 the efi"efts produced by this caufe upon the watch'< rate 

 of going. Having put on the pendulum fpring, and re- 

 placed the balance in the v\atch, lie laid the watch with 

 the dial upwards, that is, with the plane of the balance 

 horizontally, and in fuch a pofition that the balance when 

 at its place of reft ttiould have its marked fide towards the 

 north ; in this fituation it gained j' 35" in 24 hours. He 

 then changed its pofition, fo that tlic marked fide of the 

 balance when at reft fllould be towards the fouth, and in 

 24 hours it loft 6' 48" ; producing-, by its change of po- 

 fition only, a diflerence of 12' 23" in its rate. This dif- 

 ference mull be ftill further augmented or diminifhcd as 

 the wearer might happen to carry in his waiftcoat pock- 

 et, a key, a knife, or any other article made of fteel. 

 Subttituting, in the room of the ttecl-balance, one made of 

 gold, he found that the watch's rate of going was af uni- 

 form as that of any watch on the like conftruclion. 



Balance, Hyi'rnflaUral, in Hydraulics., is an inftrument 

 for determining the fpecific gravities of bodies. Sec Hv- 

 DROSTATiCAL, and Specific Gravity. 



Balance of Forces, in Mechanics. See Compound 

 Motion. 



Balance, in the Accmtnts of Merchants, is, when the 

 debtor and creditor fides of any diftincl account are equal. 

 In fuch cafe the account is faid to be balanced. 



Balance of p merchant, or trader's books, is a branch 

 of the art of accountantlhip. In the method of keep- 

 ing the books of traders, according to that excellent 

 art of charge and difcharge by double entr\-, fucli 

 books, if corretlly kept, will always be fit for a general 

 balance. For fuch is the excellency of that method, that 

 the books of themfclves mull ncceflarily balance on the 

 whole, though not in every diftincl account throughout 

 the ledger. See Book-Keeping. 



Balancf, among Painters. See Eqi'ILibrium. 

 Balance of the Conjl'itution, in Political Oeconomy, de- 

 notes the fecurity which each part of the legillature pof- 

 fefles in the cxercifc of the powers aftigEied to it from 

 the encroachment of the other parts. The political equi- 

 librium fignified by this phrafe, eonfifts in two contrivan- 

 ces, viz. a balance of power and a balance of interefl. By 

 the former is meant, that there is no power pofttfTcd by 

 one part of the legillature, the abufe or txccfs of which 

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