CARAT, originally, it would seem, the name given to the seeds of the Abyssinian coral flower (q.v.) or coral-tree (erytkrina Abyssinica); but these, which are small, and very equal in size, having been used in weighing gold and precious stones, C. has become the designation of the weight commonly used for weighing precious stones, and particularly diamonds. The seeds of the carob (q.v.) tree have also been said to be the original C. weights of jewelers, but with less probability.
Goldsmiths and assayers divide the troy pound, ounce, or any other weight, into 24 parts, and call each a C., as a means of stating the proportion of pure gold contained in any alloy of gold with other metals. Thus, the gold of our coinage and of wedding-rings, which contains it of pure gold, is called "22 carats fine," or 22 C. gold. The lower standard used for watch-cases. etc., which contains 44 of pure gold, is called 18 C., and so on. The C. used in this sense has therefore no absolute it merely denotes a ratio. This, however, is not the case with the C. used for weighing dia monds, which has a fixed weight, equal to 3i troy grains, and is divided into quarters, or " C. grains," eighths, sixteenths, thirty-seconds, and sixty-fourths. These C. grains
are thus lessthan troy grains, and therefore the jeweler has to keep a separate set of 'diamond weights.
CARAIrSIUS, a supposed native of Holland, of whom nothing is certainly known except that he had a conspicuous part as an ally of the Romans in the conquest and nil ing of Britain near the close of the 3d century. He had been put in command of the fleet in the English channel for the purpose of protecting the coasts of Britain and Gaul from the Frisian pirates; and his conduct had been such that the Roman emperor Max imilian gave an order for his death. C. immediately assumed the title of emperor of Britain, and held power for about seven years, his independence having been acknowl edged by the Romans, whose empire was rapidly falling into ruin. He was assassi nated at York in 293 by his chief officer and rival, Allectus, who held the imperial title for three years, at end of which time (296) Constantine Chlorus re-established the rule of Rome.