The accompanying diagrams represent a certain large diamond both in the rough and after it was cut into a brilliant, and they will help to explain the process of diamond-cutting, which is briefly as follows: The first process is to make lead models of the stone in its actual state and also in the ideal, namely, after it is cut. By this means is found out the most economical way to shape it. The next step is to cleave it toward that shape as far as possible. Cleaving is performed in two ways; by a steel saw strung on a whalebone and coated with diamond dust which saws off the required amount; or by scratching a nick with a diamond point in the direction of the grain and splitting it off with one blow. This latter process, observes an old writer, requires great strength of mind as well as dexterity of hand, for by an unlucky blow a valuable stone may be utterly ruined. Supposing however that the cleavage has been safely performed, the diamond is next fixed into a handle and is so imbedded in a soft cement as to leave exposed only that portion which is to be ground. By means of another diamond similarly imbedded in a handle it is worked down to the requisite shape. The dust from the two grinding diamonds is carefully saved and is used for polishing them. This process is effected by means of a disk of soft iron about a foot in diameter, coated with the diamond dust mixed with olive oil, and made to revolve very rapidly in a horizontal position. The portion of the diamond to be polished is then pressed against the revolving wheel and a high state of polish is thus attained. The grinding of the facets is entirely governed by eye, and such is the dexterity and accuracy attained by good manipulators that perfect roses are cut so small that fifteen hundred of them go to the carat; and when we remember that one hundred and fifty carats go to an ounce we shall have some faint idea of the minuteness of the work.[J] [J] The carat is the seed of a kind of vetch common in India, and is of such uniform weight that it naturally suggested itself as a standard measure, just as in our country the barley grain was taken as the unit. In Europe the brilliant is the usual form to give to the diamond, and the one most admired. The invention of this particular method of cutting is due to Vincenzo Peruzzi, a Venetian, who seems to have introduced the fashion in the latter half of the eighteenth century. He discovered that the utmost light and fire could be obtained by reducing the diamond to the shape of a pair of truncated cones, united at the base with thirty-two facets above and twenty-four below the girdle or largest circumference. [Illustration: DIAMOND AFTER CUTTING, TOP, BOTTOM AND SIDE.]