e Order employed. Thus the diameter of the Roman Doric should be about
one-eighth of the height, that of the Ionic one-ninth, and of the
Corinthian one-tenth (see ORDER).

DIAMOND, a mineral universally recognized as chief among precious
stones; it is the hardest, the most imperishable, and also the most
brilliant of minerals.[1] These qualities alone have made it supreme as
a jewel since early times, and yet the real brilliancy of the stone is
not displayed until it has been faceted by the art of the lapidary
(q.v.); and this was scarcely developed before the year 1746. The
consummate hardness of the diamond, in spite of its high price, has made
it most useful for purposes of grinding, polishing and drilling.
Numerous attempts have been made to manufacture the diamond by
artificial means, and these attempts have a high scientific interest on
account of the mystery which surrounds the natural origin of this
remarkable mineral. Its physical and chemical properties have been the
subject of much study, and have a special interest in view of the
extraordinary difference between the physical characters of the diamond
and those of graphite (blacklead) or charcoal, with which it is
chemically identical, and into which it can be converted by the action
of heat or electricity. Again, on account of the great value of the
diamond, much of the romance of precious stones has centred round this
mineral; and the history of some of the great diamonds of historic times
has been traced through many extraordinary vicissitudes.

The name [Greek: Adamas], "the invincible," was probably applied by the
Greeks to hard metals, and thence to corundum (emery) and other hard
stones. According to Charles William King, the first undoubted
application of the name to the diamond is found in Manilius (A.D.
16),--_Sic Adamas_, _punctum lapidis_, _pretiosior auro_,--and Pliny
(A.D. 100) speaks of the rarity of the stone, "the most valuable of
gems, known only to kings." Pliny described six varieties, among which
the Indian, having six pointed angles, and also resembling two pyramids
(_turbines_, whip-tops) placed base to base, may probably be identified
as the ordinary octahedral crystal (fig. 1). The "diamond" (_Yahalom_)
in the breastplate of the high priest (Ex. xxxix. 11) was certainly some
other stone, for it bore the name of a tribe, and methods of engraving
the true diamond cannot have been known so early. The stone can hardly
have become f