employed, to split, cut, and polish the diamond; as well also, as its applications in some of those useful and ingenious arts which add to our pleasures and relieve our necessities.

The diamond is, of all substances, the hardest we are acquainted with. It can only be cut or fashioned into any required form by abrasion, which is performed by forcibly rubbing the surface of one diamond against that of another. The diamond is found both in rolled or rounded pieces, and also crystallized. Its primitive figure is the octahedron, in which each plane is inclined to its adjacent one, at an angle of 109° or thereabouts; the facets are usually curvilinear, whatever the form of the crystal may be; but, as I shall have occasion to show that the octahedron is the form which is most usefully applied to the arts, and as a correct description of its various other mo difications in respect to crystallization is foreign to my intention, I shall not make any further observations on that head.

On splitting Diamonds.-Although the diamond is excessively hard, yet it may be separated into various pieces by splitting, which is performed by substances much softer than itself; but to effect this purpose, a blow is necessary to be given. As splitting is generally employed for one or two different purposes, I will endeavour to explain the intent of each. It is always an object of the greatest importance, when diamonds are to be cut and polished for ornamental purposes, to choose that part of the stone for the table or front, which will afford the greatest breadth; but, as some stones present so much of a spherical form, it is desirable to remove certain portions thereof by the operation of splitting, which saves the great labour of reducing or removing such portions by cutting or abrasion; and it has also the farther advantage of sometimes producing pieces, which may be cut and polished, so as to form smaller stones. The other case where splitting is necessary, is, when a stone of considerable size is so formed, that it

will split into several pieces, each sufficiently large to make a valuable stone when polished, and thus be more profitable, than if it had been worked as a single stone. This proceeding is not, however, very often resorted to, because diamonds increase so greatly in value as their size increases. When a stone is nevertheless to be broken, for the reasons just stated, it is usually separated into six pieces, the peculiar cleavage of the diamond being favourable to such a division.

When a diamond is to have a part removed or separated from it by splitting, which is a process that requires a thorough knowledge of the subject, it is fixed into a ball of cement, about the size of a walnut, the cement being warmed previously; the stone is then imbedded partly in it, taking care to leave that part uncovered which it is determined to separate. Another whole diamond, having a sharp edge, or a piece that has been split from some other stone, is then fixed in another ball of cement, letting the part which has the sharp edge protrude; and with this edge a slight gap or notch is made on the stone to be split, by a kind of sawing movement, until a groove is formed sufficiently deep to receive the extreme edge of a blunt razor blade, which being smartly struck by a hammer, while the stone is held in a favourable position, the intended piece may then be removed with considerable facility, by a person practised in the method.

The cement used for this purpose is brought from Holland, where it is probable diamond cutting and polishing were first performed in Europe. Its appearance is like the common cement formed of resin, pitch, and very fine brick dust; but it is very much tougher, and more adhesive.

Where more than one piece is to be split from a stone, the same methods of fixing, notching, and splitting, must be repeated; and then the stone is considered to be in a fit state for cutting.

It will now be evident that the diamond, although

infinitely harder than steel, may yet be broken with ease by that metal, if it be acted upon by a blow properly applied.

On cutting Diamonds. The next operation is, to give a proper form to the facets or faces (which, it must be observed, are always planes); and for that purpose, the stone must be imbedded in cement, fixed on the end of a small stick of wood; that part of the diamond being allowed to protrude out of the cement, upon which it is intended to form a principal plane, or facet.

If a diamond cutter has only a single stone to cut, he must then provide himself either with another whole stone or a piece of one; and which must also be fixed on a similar handle or stick, by means of cement; a part of the piece or whole stone being left to project, in order that it may be used to rub or abrade the surface of the stone to be cut. But it rarely happens that this circumstance, of having one stone to cut, is necessary to be resorted to; as it will be easily conceived that a great loss of time and labour takes place in such a mode of proceeding, as two stones may be cut in the same time as one only; the abrasion being generally equal, and similar on each.

When the two stones are affixed to the handles, as I have described, the diamond-cutter seats himself in front of his work-board, upon which is affixed a small, strong, mahogany box, about four inches long, three inches wide, and three inches deep. The sides of the box are half an inch in thickness, which gives it considerable strength. The upper surfaces of the four sides of the box are each covered by a rim of steel, and in the centre of each of the longest sides, a perpendicular pin of steel is firmly affixed, which pins are used as fulcra, against which the handles or sticks, holding the stones, are to be firmly pressed when in operation.

The two stones are now to be pressed with very considerable force against each other, and at the same time the sticks being also pressed firmly against the steel pins on

the two edges of the box, a rocking motion is to be given to each stick in opposite directions; the steel pins being, as above mentioned, the fulcra, or centres of motion of the sticks.

By thus rubbing the two stones against each other, the convex surfaces that are brought into contact are reduced by the continued abrasion, until they assume a roughly flat surface, or principal facet.

As that part or end of each handle that contains the diamond, or to which it is affixed by the cement, extends only about an inch or an inch and a half beyond its bearing against the steel pin, on the side of the box, it will be easily conceived, that it can only describe the arc of a circle of that radius. But the other portion of the handle, or stick, which is grasped by the hand of the workman, being much longer, it enables the operator to use it with great power, on account of its greater leverage, and which, of course, enables him to exert a very great force, that being absolutely necessary.

The mahogany box, has also a small thin plate of brass made to fit it very exactly; which, being pierced with a great number of fine holes, acts as a sieve, to let the very fine, and nearly impalpable powder pass through, which is formed by the abrasion of the diamonds against each other. The box is also furnished with a lid or cover, which the workman most carefully puts upon the box every time that he examines the facet he is producing.

This fine dust, is technically called "diamond powder," in order to distinguish it from a somewhat similar powder, which is produced by bruising the diamond in a hardened steel mortar, with a steel pestle; by which means the diamond may be separated into very fine particles and become exceedingly useful for certain purposes, which I shall explain hereafter*.

* See the description of the common steel mortars and pestles used for this purpose, and also of improved ones, with engravings of both sorts, in ou Technical Repository, Vol. VII. p. 52.

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The mode of examining the facets of the diamond, while under the process of cutting them, is by wetting it with the saliva from the tongue; but, previous to doing this, the adhering diamond-powder is most carefully brushed off from it, with a small short-haired brush.

It may, perhaps, seem superfluous to state, that when: one facet or flat surface is produced upon each stone, in the manner above described, they are shifted in the cement, which, for that purpose is warmed over a candle; and the stones are then so placed as to bring each into a position to have another principal facet formed thereon; and when all the large facets are formed that are necessary, this department, technically called “ cutting," is completed.

On polishing Diamonds. Having now explained two of the great and principal divisions of this art, namely, those of splitting and cutting, I have to treat of the third and last branch of it for ornamental use, that of polishing; by which the wonderful lustre that is possessed by this peculiar substance only, is brought out, to delight the ravished eye of the beholder, when properly set by the skill and taste of the jeweller.

As the methods of fixing and holding the diamond for the purpose of polishing it, are different from those I have above described in the process of cutting, I shall proceed to give a particular description thereof.

A small hemispherical cup, made of copper, and filled with soft pewter solder*, is placed upon a charcoal fire, and the solder being barely melted, the cut diamond is placed upon the surface of the solder, and the workman presses it down, and imbeds it so deep that he is enabled to bring a small quantity of the melted solder, over or around the upper part of the stone, by which it becomes nearly enveloped in the mass of metal; one of the large facets, which have been produced by cutting, being the only part of it which is left uncovered and exposed to view.

* One of the fusible metals would seem to be peculiarly fit for this purpose.-EDITOR.