MR. HAKDY's BAN^KIWJ.^^ 115 



I nv adjuftmj^nt .at;, the balance;, to accommodate itfelf to, the ^ 



viianges made in the ipring, and other parts connetled \vJkh 

 it. Hence it became necelfary, that fome means fhould.be 

 uied to ft op the-, balance at certain limits beyond its natural 

 arch of vibrali(>w ^ qixd various attempts have, ■ been , made. to 

 <itihc\ it. One. w§X-'iSi. by a f^ov^jable pief;^,,'a|a t^ axU .of f'o'^"^«r .'"ethoda 

 the balance, which banks againft a pin, y«t lb as,. to. fuffec 

 the balance to vibrate more than 300 degrees. Another me- 

 thod, is to have a; piece, rnoveable on a,oeqtre in. one of the 

 arm!; of the ba'ance, and applying itfelf as a tangent to the 

 pendulum-fpring, which paiftis through a hole in the pipce. 

 It has aifo a_knee, which almoll touches the, plate, and; juft 

 pallcs fr^e..of ^', pin placed in it. But when the balanc^e vi- 

 brates fo a* |k> approach its utrnpll , limits, the yaclion of, th^ 

 fpring, vvhii<; in. a ftate of unwinding, throws the piece out- 

 ward, -io as to fall in the way of the pin, and flop tlie balance 

 from proceeding farther. Another mode is by a ftraight fpring, 

 fcrewed ujK)n.the plate, having a hook at the end of it, into 

 which a pin placed in the balance ftrikes, when, as before, 

 the pendulum-fpring, in unwinding, touches the iiraight 

 fpring, and moves it a little outwards. There is alfo a way 

 of bankipg by means of a bolt, which is thrown back by the 

 pendulum-fpring, and made to fall in the way of a pin placed 

 in the rim of the balance. Thefe are the principal modes of They are ob- 



bankinor now in ufe, and they do not differ materially from J^*?^^,^" ^5°?.- 



^ , ' . ^ . ^ ^ weight and fnc- 



one another in principle. But the weight and fridion of fo tion. 



many pieces, on fo delicate an organ as that of a pendulum- 



ipring, are perhaps nearly as hurtful to the time-keeper as the 



injury it may fuftain when it is left without any banking 



whatever. 



In Figures 1 and 2, Plate VI. the fame letters are placed, Defcrlptiofl, 



to fiyjnify the fame things. A A is the balance to which the ^'^1^ reference 



? I r • • r n 1 • I r i t . , to the engravi«s, 



pendulum-iprmg is taitened in the uliial way. In one or the 



crofTes of the balance is placed a pin P, which Hands 'a little "' ' 



way above its furface ; and when the balance is caufed to 



vibrate a complete circle, the pin in its motion will defcribe 



the dotted circle P O Q, and juft pafs clear of the iniide of 



a projection formed on a cock B> which is fattened on the 



plate by means of a fcrew. At about one-fourth of a turn of 



the pendulum-fpring, reckoned from its ftud E, is p'aced a 



very delicate tapering piece of fteel S, having a finall, hole in 



12 it. 



