RULE OF THREE is the technical term for that rule in arithmetic, otherwise called proportion which teaches the finding of a fourth number proportional to time given numbers. The term "rule of three" has been in use from the commencement of the 16th c.; and from the great utility of the operation in commercial transactions, it received, almost from the commencement, the name of the Golden Rule (q.v.). To the ordinary "rule of three" was added the betel,•er rule, or "rule of three inverse" (cor responding to inverse or reciprocal [q.v.] proportion), and the " double rule of three," in which two or more ratios are given as determining the number to be found.
RUM, a mountainous island of Argyleshire, belongs to the group of the Inner Heb rides, 15 in. n.n.w. of Ardnacmiimrchan Point. It is 8 m. long, about 7+ in. broad; area upwards of 30,000 acres, only about 6 per cent of which is under cultivation. Pop. '51, 162; '71, Si. The islana is a mass of high sharp-peaked mountains, rising in Ben More to the height of 2,320 feet.
RUM, a kind of spirit made by fermenting and distilling the "sweets" that accrue in making sugar from cane-juice. The scummings from the sugar-pans give the best runt that any particular plantation can produce; scummings and molasses, the next quality; and molasses the lowest. Before fermentation water is added, till
the "set" or wort is of the strength of about 12 per cent of sugar; and every ten gallons yields one gallon of rum, or rather more. The flavor of rum depends mainly on soil and climate, and is not good where canes grow rankly. Pine apples and guavas are at times thrown into the still, but on the great scale, no attempt is made to influence flavor artificially. The finest-flavored rums are produced by the old-fashioned small stills. The modern stills, which produce a strong spirit at one operation, are unfavor able to flavor. The color of rum is imparted after distillation by adding a certain pro portion (varying with the varying taste of the market) of caramel, or sugar melted with out water, and thus slightly charred. Rum is greatly improved by age, and old rum is often very highly prized; at a sale in Carlisle in 1865, rum known to be 140 years old sold for three guineas per bottle. It forms a very important part of our colonial prod uce: the quantity imported into Britain in 1875 was 8,815,681 gallons (home consump tion, 5,361,486), valued at £1,014,456. Rum is distilled both in the East and West Indies.