The general position of the stick is nearly vertical, so as to keep the surface of the stone inclined just sufficiently to prevent the stem of the tool coming in contact with the face of the stone. In dotting the outline, or cutting shallow works with large tools, the stone may be held quite horizontal; but in cutting deep and delicate works, or sharp angles, very small tools must necessarily be employed, and the stone then requires to be considerably inclined, in order to allow the edge of the tool to penetrate to the bottom of the cavity, without risk of the stem being brought in contact with the surface of the work.

In all cases in which the stone can be kept horizontal, the process of gem engraving is comparatively easy, and the principal difficulties that are met with, occur in cutting the curved outlines, and in making a sunk surface quite flat. As previously mentioned, the edges of sunk surfaces should be made nearly perpendicular, to give definition to the impression, and the outlines are cut with a thin tool like fig. 1201, in which the face of the tool is flat, but, to give strength, the back is necessarily made conical.

In those cases in which the flat face of the tool can be applied to the convex side of a curved recess, no material difficulty is experienced in cutting the outline nearly perpendicular, as the stone can be slowly, but continuously, twisted round, to bring every successive part of the curve in a direct line with the flat face of the tool, and should the edge of the outline be irregularly cut at the first attempt, a second cut may be taken with a smaller tool in the same manner, to correct the irregularities of the edge, and during the entire process the tool and work remain constantly under observation. But it will be readily conceived that the flat face of the tool cannot be so conveniently applied to the concave side of the recess, as the edges would have a continual tendency to encroach upon the curved line, and therefore, in cutting around the concave side of a curve, the conical back of the tool must be made to traverse around the inside of the curve, but the back of the tool being less under observation than the face, it is much more difficult to cut the edge smoothly, and in any attempts to correct the irregularities with a smaller tool, it is necessary to adopt the same course of applying the back of the tool to the concave edge of the work, as it is found that when the edge has been cut with the back of the tool, the face cannot be successfully applied to rectify any minute errors.

The difficulty of making a sunken surface quite flat, arises from the circumstance that the entire face has to be produced with only a very small portion of the edge of the tool, and without any mechanical guidance being derived from the tool itself. For although the edge of a tool, such as fig. 1202, may be turned very nearly flat, still on examination after being used, it will always be found rather convex, owing to the circumstance that the edge has a constant tendency to wear the fastest at the margins, and the rounded edge of the tool has, of course, a continual tendency to cut the surfaces to which it is applied into a series of small hollows, instead of one continuous plane.

In flattening a sunken surface, or, as it is sometimes called, stippling, the difficulty is overcome by keeping the stone in continual but steady motion. The stone being quickly traversed with very short strokes beneath the tool, the entire surface is successively passed under the lowest point of the tool, which is only allowed to cut at the highest points of the surface, and these are determined apparently by intuition, so delicate is the sense of feeling acquired by the best gem engravers; but, as may be imagined, this great dexterity of hand is only to be acquired by long and patient practice.

When the stone requires to be much inclined from the perpendicular, to allow small tools to penetrate into the minute details of deep works, the difficulties of gem engraving are materially increased. As previously mentioned, some of the little disks are less than one hundreth of an inch in diameter, while, to afford sufficient stiffness to the tool, the diameter of the stem requires to be about one eighth of an inch at the back, and the front end is made conical for about 1 inch of its length from the disk, as seen in the greatly enlarged section, fig. 1207. To enable these small tools to penetrate even into a flat surface, it is obvious that the stone must be inclined to a greater angle than the cone of the stem, or the latter would rub on the flat surface; but in finishing a deep corner, so as to make it quite square and sharp at the bottom, the stone must be inclined to a much greater angle, and in consequence, instead of the tool cutting perpendicularly downwards, it cuts obliquely, at the same angle as that at which the stick is held, and this tendency of the tool requires to be overcome by the tact of the artist.

In the case of squaring a corner, there is generally sufficient room in the sunken portion to allow the entire disk to be inserted within the cavity, upon the side of which it is principally required to operate, and the surface of the stone may be held nearly vertical. But in cutting fine lines on a deep surface, such as some of the finishing lines in the hair of a deeply sunk head, the lines do not admit of being made much wider than the edge of the tool. Very delicate management is required to sink these lines perpendicular to the general surface, and the stone must be applied to the tool so as to commence the line a little above the exact position for the center of the line, in order that the oblique cut, when made to the appropriate depth, may terminate in the desired position.

In ordinary seal engraving, great accuracy of finish in the details is never attempted, and these difficulties of manipulation are not severely felt, but they are a great obstacle to the practice of the higher department of gem sculpture, which not only requires the artist to possess great talent for the conception of beautiful designs in sculpture, but he must also devote many years to the attainment of sufficient mechanical dexterity, to enable him to realise in detail the conceptions of his mind. The gem engraver also labours under the further disadvantage, that from the minute and delicate character of his works, they can only be properly appreciated by those few persons who have carefully studied the subject.