I'AKINO. 



HAL A 



mon. InotW para of TurkeT.ai*luUWU, it U prolonged by th* lower 

 onlcf* at ls^ for five or six days, or even lunger. The Moood festival, 

 4m^"i"-t~' J<ialA*4. or A'.rfcU A.inl, that U. " the festival of 

 UM -crince*," ii instituted in commemoration of Abraham offering 

 hi* son Isaac, and it celebrated seventy day* after the former, on the 

 IDlh of lhu'lhjja, the day appointed for slaying the victims by the 

 pilgrim* at Mecca. It lasts Uirw dy. the fint being the mo*t*olemn 

 day of the pilgrimage, but a* the ceremonies are only imitations of 

 what take* place at Mecca, it U obeerred with much less strictness, and 

 ha*, therefore, obtained the name of the Lower Bairam. At each of 

 the** festivals but one Wrta U read, that is, divine Mrvioe U only 

 one* publicly performed, on the fint day, about an hour after sunrise ; 

 and in the Turkish empire eren this solitary act of public worship is 

 now no longer announced by the muezzins, or public criers, from the 

 top* of the minareU or turret* of the mosques. At Constantinople the 

 two p-ji4m. are celebrated with much poinp. The sultan on this 

 occasion receives the homage of the different orders of the empire, and 

 proceeds in state, followed by all the higher officers, to the mosque. 

 As the Mohammedans have a lunar year of 354 days, the two festivals 

 run, once every thirty -three yean, through all the seasons. 



(Sale's Koran, Preliminary Discourse, s. vii.) 



BAKING. [BREAD ; ENAMELLI.VO ; GLASS-MANUFACTURE ; POTTERY.] 



BALANCE, a corruption, probably, of the middle Latin word 

 I'alrmtia, used (see Ducange) to denote price or value ; whence came 

 nrfimrr, mentioned by the same author, who consider* the word 

 Jfit *y or BHanx, to be a re-constniction from the common idiom. 

 The word baUaxfia is found in the 13th century. From meaning the 

 worth or value, it came to signify any instrument used for ascertaining 

 it, but particularly when weight was the quality referred to. Hence 

 came the general meaning of the term, in which it stands for any state 

 of things under which opposing circumstances just destroy the effects 

 of each other; as when we speak of a balance of power, of good and 

 evil, 4c. Hence also the commercial meaning, in which the balance 

 is not the state just mentioned, but the sum of money which must be 

 added to one or the other side of an account, in order that the debts 

 and credits may be balanced, or of equal amount. As an instrument 

 of common use, the term Scale* is more frequently applied. In 

 phiV~yh'"l apparatus, the word is applied to any machine by which 

 an effect is measured, at the pleasure of the inventor, for there is no 

 other rule. Fur the hydrostatical balance, see GRAVITY, SPECIFIC ; for 

 the torsion balance, see TORSION, 4c. [STEEL-YARD, LEVER, COIN 

 WKIGUIXG- MACHINE, SI-RING- BALANCE.] 



The instrument most commonly known by the term balance is a 

 superior sort of scales, executed with all the precision necessary for the 

 nicest operations of physics, and particularly of chemistry. We shall 

 therefore confine ourselves to a statement of the circumstances which 

 are necessary to a good performance of the philosophical balance. 



A simple straight lever, balanced by weights resting immediately 

 upon it, so that the centre of gravity fall on the fulcrum, is at rest in 

 every position : for no motion will change the position of the centre 

 of gravity. The same may be said when some of the weights hang by 

 strings ; firstly on the mechanical principle that any force may act at 

 any point of iU direction, and secondly, by a geometrical theorem, 

 which points out that when weights either hang by strings from 

 different points in a straight line, or when some are on the straight 

 line, and others hnging from it, if the centre of gravity of all the 

 weights be Jever in the same vertical with the fulcrum, no motion 

 round the fulcrum can remove it out of that vertical : and all that 

 is necessary to a perfect equilibrium is, that the centre of the 

 weights (that of the machine included), should fall directly under the 

 fulcrum. 



The preceding statement rests upon the hypothesis of a system so 

 contrived, that every weight shall hang as it were by a string, and 

 from a straight line, so that all the strings shall approach to, or recede 

 from, the vertical passing through the fulcrum, at the same time and in 

 the same proportion. But if the line from which the weights hong be 

 bent, or if any weight be so attached to the system that it cannot be 

 considered as hanging from a given point, the equilibrium which 

 subsist* in one position will not subsist in another. And this, namely, 

 that there should be only one position of equilibrium, is not only 

 required for the use of the instrument, but practically necessary in its 

 construction, as an indi/erent balance, like that just described, would 

 be difficult of execution. 



A balance should be tentiUe, meaning that, when poised, a very 

 small addition of weight to either scale should make it turn that is, 

 overcome the necessary friction and adhesion of the pivot or knife- 

 edge on which it rests. If there were no friction, the smallest weight 

 would make it turn. The first condition of sensibility, therefore, is the 

 diminution of friction to the utmost possible extent This is done by 

 making all the parts of a high polish, and by placing the beam upon 

 the support by means of knife-edges attached to its sides. But in 

 order that the knife-edge may not become blunt, the beam is not 

 allowed to rest upon the support except when the instrument is in use; 

 at other times it u raised by two arms which just remove the knife- 

 edge off the support, and these arms can be let down by means 

 of a handle. We shall presently come to the other conditions of 

 sensibility. 



A balance should aUo be KaUt, that in, it should, on being disturbed. 



immediately return and oscillate about the position of rest This is 

 done bv making the centre of gravity of the whole apparatus fall 

 below the point of support But as stability is not so difficult to attain 

 as sensibility, the Utter must be most attended to. The scales in the 

 shops are sufficiently stable, but few are very sensible. 



Neglecting the particular nature of the method of lupport, and 

 circumstances of mere confirmation, the balance may be represented as 

 follows (see Whewell's Elementary Mechanic* :') 



c is the point of support, showing a section of one of the knife- 

 edges, which rests upon a smoothly-polished plane ; o the centre of 

 gravity of the whole beam, A and B the points of suspension of the 

 scales (which are also usually on knife-edges), D the point of coincidence 

 of A D and oo. The stability of two balances is thus compared. 

 Suppose that the same small disturbance be given to both, say the- 

 beam is inclined one degree in both. Then if the force with which 

 the first endeavours to recover its position be double or triple that 

 of the second, the stability of the first is double or triple that of the 

 second. To compare these forces, construct the following formula for 

 both. 



To u-fl'j/it of both tcalet x CD add weight of beam x CO. 



For instance, suppose two balances as follows : 



Then will the stabilities of the first and second beaa24x2-t-30xlto 

 30 x 3 + 50 x 2, or as 78 to 190. 



The sensibility is estimated by comparing the angles through which 

 very small equal weights would incline the balances. If, for example, 

 a grain put into a scale of each inclines the first four degrees, and the 

 second only two degrees, the first is twice as sensible as the second. 

 To compare the sensibilities, multiply the length of the arm of each by 

 the number which represents the stability of the other in the formula 

 just given. Thus the sensibilities of the preceding balances are as 

 12 x 190 to 14 x 78, or as 2280 to 1092. 



It would not be worth while to work very accurately by the 

 preceding formula ; but the general rules deducible from them are 

 valuable. 



1. Other things remaining the same, the longer the arm the greater 

 the sensibility. 



2. The arm having a given length, every increase of sensibility is a 

 decrease of stability, and rice vend. 



3. Additional weight, either to the scale or beam (the arm re- 

 maining the same), is favourable to stability, and unfavourable to 

 sensibility. 



4. Whatever does not alter the length of the arm cannot be favour- 

 able to both. 



In all that precedes, it must be recollected that in the weight of the 

 scales is included whatever may happen to be in them. Consequently 

 every balance has different degrees of sensibility and stability, with the 

 different weights which are employed. But as, generally speaking, the 

 quantities weighed in delicate balances are small, a balance which is 

 highly sensible when no weight is in the scales, will be so for every 

 weight with which it is intended to use it A balance made by 

 Ramsden for the Uoyal Society, weighing ten pounds altogether, 

 turned with the ten-millionth of that quantity, or with about the 

 thousandth part of a grain. 



A balance should be made as much as possible of brass. Steel and 

 iron are apt to acquire magnetic properties. It should also be inclosed 

 in a glass case, with doors for communication ; and, when not in use, 

 a portion of muriate of lime, or any other strong absorbent of moisture, 

 should be placed in the case. A needle is usually attached to the 

 beam, which points either exactly upwards or downwards when the 

 beam is horizontal. A graduated scale of degrees is attached to the 

 frame-work of the instrument, in such manner that the needle may 

 point to zero when it is vertical. The oscillations of the balance, li.-ii 

 the centre of gravity is near to that of suspension, will be very slow, 

 and by means of the needle it may be ascertained, before the balance 

 comes to rest, whether horizontal equilibrium lias been obtained : for 

 in that case it will describe equal arcs on the graduated scale on each 

 side of the zero point ; while if either scale be overloaded, the needle 

 will move through more degrees on the sido of that scale than on the 



