Page:The American Cyclopædia (1879) Volume II.djvu/254

 234 BALANCE rect results. The weights employed for deli- cate balances are either troy grains, one of each of the units, one of each of the tens, and the same of the hundreds and thousands, as also of the tenths, hundredths, and thousandths of a grain ; or they are the French gramme weights, with their decimal parts. The latter are the most commonly used in chemical assays and analyses. The larger weights are of brass, the smaller of platinum, nd these are always handled by means of a pair of forceps. The beam of the balance is, according to the meth- od introduced by Berzelius, frequently marked by divisional lines into tenths, and one of the small weights, as a tenth or hundredth of a grain, or a milligramme, is bent into the form of a hook, so that it may be moved along the beam to any one of these lines to bring the balance to exact equilibrium. By this arrange- ment the picking up and trying one weight after another is avoided, and the proportional part of the weight used is that indicated by the decimal number upon the beam at which it rests to produce equilibrium. The best ma- terials for a balance are those which combine strength with lightness, and are least liable to be affected by the atmosphere and acid vapors. Brass, platinum, or steel is used for the beam ; but probably aluminum will prove to be better adapted for this purpose than either. The pans are commonly of platinum, made very thin, and suspended by fine platinum wires. The support is a brass pillar secured to the floor of the glass case in which the instrument is kept. Doors are provided in front and at the sides, by which access is had to the instru- ment; but these are commonly kept closed, and are always shut in delicate weighing, that the beam shall not be disturbed by currents of air. So delicate are the best balances, that when lightly loaded and left to vibrate, they may be affected by the approach of a person to one side of the glass case, the warmth radi- ated from the body causing the nearest arm of the beam to be slightly expanded and elon- gated, so as to sensibly preponderate. The degree of sensibility is estimated by the small- est weight in proportion to the load that will cause the beam to be deflected from a horizon- tal line. It is said that a balance is in posses- sion of Bowdoin college, Maine, which, with a charge of 10 kilogrammes in each scale, is sen- sitive to -f$ of a milligramme. Becker and Sons of New York made the balance ; and they make ordinary chemical balances which with one kilo- gramme in each scale are sensitive to one tenth of a milligramme ; their small balances now in use in the assay office, New York, show a dif- ference in load of less than -^ part of a mil- ligramme. The torsion balance, invented by Coulomb to measure minute electrical forces, is still more delicate than the best beam balance. It consists of a brass wire, hung by one end and stretched by a light weight, carrying at its lower end a horizontal needle. Any force ap- pliad to one end of this needle, tending to rotate BALANOUINI it horizontally, will be measured by the angle through which it causes the needle to move ; that is, by the torsion of the wire. (See ELEC- TRICITY.) The steelyard, the Roman statera, is one of the forms of the balance, the two arms being of unequal length, the body to be weighed being suspended in a pan or otherwise from the short arm, and the counterpoise, which is a constant weight, being slid along the longer arm until equilibrium is established. As this occurs when the weight on one side multi- plied by its distance from the fulcrum is equal to the weight on the other multiplied by its distance from the fulcrum, and as on one side the weight is constant, and on the other the distance from the centre of motion, the un- known weight must be determined by the dis- tance of the constant weight from the centre. The Danish balance differs from the common steelyard in having the counterpoise fixed at one end, and the fulcrum being slid along the graduated beam. The graduation commences, at a point near the counterpoise, at which the beam with the pan suspended at the other end is in equilibrium, and the numbers increase to- ward the pan. A balance called the bent lever is employed to some extent for purposes not requiring extreme accuracy. The pan is at- tached to one end of the beam and the other carries a constant weight. From the bent form of the lever this weight is raised to a height varying with the weight placed in the scale pan. A pointer attached to the constant weight and moving along a graduated arc indicates by the number at which it stops the weight of the body in the scale pan. Its indications are the least to be depended upon when the constant weight approaches to the horizontal or vertical line passing through the centre of motion. The scales generally used in the United States for weighing loaded wagons and canal boats are modifications of the steelyard, wherein the weight of these ponderous bodies is divided by means of levers, and a known fraction of it sustained by one end of a beam, the other end of which is graduated for a moving weight. Modern modifications of the steelyard contain a pan hung at the end of the arm to receive larger weights, while the sliding weight is used only to balance the fractional parts. Spring bal- ances are popular instruments, and consist of a helix of wire enclosed in a cylinder. The body to be weighed is suspended to a wire passing up through the centre of the helix and fastened to the upper coil, which carries a pointer down a narrow slit in the cylinder, thus indicating the weight on the graduated sides of the cylinder. i:l.M.IIM. or Bangingee, an islet of the Ma- lay archipelago, in the Sulu group, claimed by Spain as part of the province of Zamboangan in the Philippine island of Mindanao, in lat. 5 57' 30" N., Ion. 121 39' E. It is about 3 m. long and 1 broad, and gives its name to the most daring Malay pirates. In 1848 it was captured by the Spaniards, who had 11 officers and 170 men killed and wounded ; 450 of the