B A L 



213 



B A L 



Balance, tion. The circular ends of the beam are excavated 

 in the middle of their thickness, on the lower side, a 

 good deal above the centre : the axis is fastened in 

 the two sides of the circular ends, with its sharp edge 

 upwards a little concave, having passed through a 

 piece of hardened and polished steel of the shape of 

 an 8 ; the inner edges of the two eyes being worked 

 to sharpness : by the upper eye it hangs upon the 

 axis within the part excavated, forming the point of 

 suspension, and with the lower the scale-strings are 

 connected by a ring. A piece of wire extending 

 above the centre is worked into a screw, and upon 

 this an adjustable ball of brass is placed for the pur- 

 pose of procuring quick or slow vibrations. Oppo- 

 site to this, extending downwards, is a long index 

 pointing to a graduated scale of ivory for ascertaining 

 the position of the beam. The lever below is fixed 

 to the pillar, and by its action lowers the beam until 

 the pans rest upon the bottom of the glass case, or 

 raises it when in use. At the top of all there is a light 

 index of brass-wire, which, by being turned round 

 with the finger, serves to adjust the index below to the 

 zero of the ivory scale : this, insignificant as it ap- 

 pears to be, is extremely convenient in practice. 

 This kind of beam is adjusted, respecting equality of 

 length in the arms, by the hammer, and bent by the 

 hand for bringing the three points of action into a 

 right line. ( E. T. ) 



An ingenious balance constructed by Messrs 

 Miller and Adie for Mr Jardine, is represented in 

 Fig. I. of Plate LI I. where A A is the beam forged 



Plate LIT. of one piece of steel, which, in order to give greater 



Miller and 

 Adie's ba- 

 lance. 



Fig. I. 



'6- 



strength with lightness, has the form of a rhombus, 

 whose acute angles coincide with the centres of sus- 

 pension B, B. Theends of the arms pass through the 

 pieces C, C, which are hollow, to receive the two 

 rings D, D, from which the scales are suspended, and 

 terminate in slender points, which serve as indexes to 

 point out the inclination of the balance on the ivory 

 arches EE. The axis or centre of support /'is about 

 2\ inches long, 1 inch deep, and three inches thick. 

 Its under edge, worked away to form a right angle, 

 passes through a box g in the middle of the beam, 

 and is fixed in its place by 10 small steel screws. The 

 edge of the centre turns on hard and highly polish- 

 ed steel plains h, from which it is lifted, when not 

 used by Y's, which are moved up by turning the 

 pinion I, which works in a rack within the hollow 

 brass pillow that forms the stand for supporting the 

 balance. Fig. 2. shews the pieces C, C on a large 

 scale, that the different parts may be more distinctly 

 seen. The rings D, D, which are hardened and well 

 polished, are just allowed to move freely between the 

 four hardened steel points screwed through the sides 

 of the pieces C, C. One of the end centres C i3 fix- 

 ed, and the other is made to move in a slit to or 

 from it, by the four adjusting screws k. The balance 

 is inclosed in a mahogany case with a glass front, to 

 the back of which is attached the brass frame L, 

 moveable up or down by a rack and pinion M, so as 

 to stop the scales, and thus check the vibration of 

 the balance when in use. The cross revels N on the 

 bottom of the pillar, are intended to adjust the plains 

 on which the centre turns, to a true horizontal posi- 

 tion, by means of the four screws O, that form the 



feet of the mahogany case. In performing the adjust- 

 ments of the balance, we must begin by placing the 

 edges of the three centres in a straight line as nearly as 

 possible, by pressing down the centre^/* with the two 

 screws p, which, if lower than the centres of suspen- 

 sion, will be known by the balance preponderating to 

 either side. In order to adjust the centre of gravity, 

 so as to be just under the centre of support, the rings 

 must be removed from the ends of the beam and the 

 slider q, and moved up as long as the beam willlibrate. 

 When it is too high, either end of the beam on being 

 depressed, will remain in that situation. We must 

 next try if the arms have equal lengths, by replacing 

 the rings and suspending the scales, and then putting 

 equal weights into them. If the balance now remains 

 in equilibrium, the adjustments are complete ; but if 

 either side preponderates, that arm is longer than the 

 other, and the moveable centre must be altered ac- 

 cordingly by the screws k. The previous adjustments 

 must now be repeated, as every alteration, in a deli- 

 cate balance, in a greater or lesser degree affects all 

 the others, so that they can only be attained by ap- 

 proximation. A balance of the above construction, 

 which we have tried, was sensible to -,-i^ of a grain, 

 when loaded with 10,000 grains in each scale, (y) 



For further information on the subject of balances, 

 see De La Hire, Mem. Acad. Par. torn. ix. p. 42. 

 Roberval, Mem. Acad. Par. torn. x. p. 343. Euler, 

 Comment. Petrop. torn. x. p. 3. Magellan, in Ro- 

 zier's Observations, torn. ii. p. 253. torn. xvii. p. 44, 

 432. Ramsden, in Rozier's Observat. torn. xl. p. 

 432. Shuckburgh, Phil. Trans. 1798, part ii. Ni- 

 cholson's Chemistry, chap. vi. Ludlam, Phil. 7'rans. 

 toI. Ix. 1770, p. 205. Ludicke, in Gilbert's Jour- 

 nal, vol. i. p. 323. Andrews, Repertory of Arts, 

 vol. xi. p. 16. Prony, Annates de Chimie, vol. xxxvi. 

 p. 3; and Nicholson's Journal, vol. v. p. 313. Guyton, 

 Annates de Chimie, vol. xlii. p. 23. Atwood, Gil- 

 bert's Journal, vol. iv. p. 148. Dillon, Mem. de I'ln- 

 stitut. Nat. torn. iv. Ferguson's Lectures, vol. ii. p. 

 385. See also Hydrodynamics, Mechanics, and 

 Specific Gravity, (o) 



BALANCE, Hydrostatical. See Hydrody- 

 namics. 



BALANCE, Torsion, invented by Coulomb. 

 See Torsion. s 



BALANCES in Timekeepers. See Chrono- 

 meters. 



BALANCERS. See Entomology. 

 BALANTES, the name of a tribe of negroes, 

 who inhabit a tract of country about 10 or 12 leagues 

 long, to the north of the isle of Bussi, in West Lou. 

 17 10', and South Lat. 1 1 45'. The Balantes have 

 no intercourse whatever with their neighbours They 

 carry on a considerable trade with the foreigners who 

 enter their roads, in rice, millet, culinary vegetables, 

 oxen, goats, poultry, and particularly gold. The 

 gold, which is of a very superior quality, is supposed 

 to be obtained from mines in the interior of the coun- 

 try. They pay a tribute in gold to the king of Ca- 

 samanca. In 1696, the Portuguese, joined by 300 

 Bissaux, attacked the Balantes, but were completely 

 defeated, and lost the whole of their baggage. Se- 

 veral Europeans, who have landed among the Ba- 

 lantes with commercial views, have been plundered 



Balance 



II 

 Balantes. 



