Page:Handbook of Precious Stones.djvu/76

the locust-tree, Ceratonia siliquu, weighs on the average 31/6 grains, and constitutes, no doubt, the true origin of the carat.

The carat is not absolutely of the same value in all countries. Its weight, as used for weighing the diamond and other gemstones in different parts of the world, is given, in decimals of a gram, by the majority of the authorities, as—

Madras ·2073533

Vienna^[1] ·20613

Frankfort ·20577

Brazil and Portugal ·20575

France ·2055

England ·205409

Spain ·205393

Holland^[2] ·205041

Assuming the gram to correspond to 15·43235 English grains, an English diamond carat will nearly equal 3·17 grains. It is, however, spoken of as being equal to 4 grains, the grains meant being "diamond" grains, and not ordinary troy or avoirdupois grains. Thus a diamond grain is but ·7925 of a true grain. In an English troy ounce of 480 grains there are 1511/2 carats; and so it will be seen that a carat is not indeed quite 3·17 grains, but something like 3·1683168 grains, or less exactly, 3·168 grains. Further, if we accept the value in grains of one gram to be, as stated above, 15·43235, and if there be 1511/2 carats in a troy ounce of 480 grains, it will follow that an English diamond carat is ·205304 of a grarn, not ·205409, as commonly affirmed. By recalculating the value of the diamond carat, as used in different parts of the world, into its scientific equivalents in the metric system, the weight to four places of decimals will become, according to Mr. Lowis D'A. Jackson^[3]—

Turin ·2135

Persia ·2095

Venice ·2071

Austro-Hungary ·2061

France ·2059

Portugal and Brazil ·2058

Germany ·2055

England and British India ·2053

Holland and Russia ·2051

Turkey ·2005

Spain ·1999

Java and Borneo ·1989

Florence ·1965

Arabia ·1944

Egypt ·1917

Bologna ·1886

---

1. Schrauf gives ·2057.
2. Schrauf gives ·20613.
3. Modern Metrology, p. 377.