The Diamonds
occupy the highest rank among precious stones, and possess an intrinsic
value in almost every part of the globe. The discrimination of the
various qualities, colors, &c., which exercise an immense influence
over their value is very difficult, and can only be acquired by
experience ; the size can be ascertained by the table in the present
work, the defect by close observation; b'ut the color, whether a
Diamond belongs to the first or second water, must be found out by
comparison with other stones ; for a brilliant may, by first
appearance, be of the whitest color, still, on comparison with another
whiter brilliant, be different by several shades. The value of the-
rough Diamond is calculated at half its weight, from the presumption
of losing 50 per cent, in cutting and polishing, and the color, size
and form of crystal establish its price. A rough Diamond, weighing
under two carats, ranges from £2 10 to £5 per carat; but . in
purchasing rough Diamonds great caution is required, as other colorless
precious stones are often mixed with them.
The
value of cut and polished Diamonds is subject to a similar scrutiny;
but Jeffries' tables, published in 1750, which are based on the
assumption that a Diamond increases in value in proportion to its
weight in the ratio to the square of its weight, that is to say,
supposing the value of a one carat stone be £8, one of two carats will
be worth 2x2x8 = £32, and
continue the same mode of calculation up to stones of 100 carats,
have, at the present date, no effect, although in former times very
practical. The reason is, that from various causes, such as the
increase of duties and taxes in the United
