It sometimes occurs that a piece is broken out of a glass, without leaving any crack to commence from; in this case, one must be made, by heating the edge (one formed by the fracture, if possible), with the iron or pastile, and instantly applying the moistened finger. When a crack is formed which may be used as described above, care must be taken not to cause an extensive fracture, which may run across the intended line of division; this may be avoided by commencing the crack at some distance from the line, and by applying the heated point for a very short time, preferring to make two or three unsuccessful attempts rather than to hasten the operation, and risk the destruction of the glass. When a glass vessel has been thus divided, the edges are sufficiently sharp to cut the fingers in handling, and are usually wavy; it is therefore necessary to make them smooth and even. The most ready way of doing this is, by grinding them down on a flat sandstone or ordinary paving-stone, with a little sharp sand or emery, and water, taking care to move the glass in a circular direction, and not merely backwards and forwards; the smoothness of the whole will depend entirely on that of the stone, and on the fineness of the sand or emery employed. If, from any irregularity, there is much glass to grind away, it is preferable to commence with sand, and finish with emery on a smooth stone; if the edges are not thus ground down, they should have the sharp angles, which are really dangerous, removed by a fine file, which should be moistened with oil of turpentine or camphine, as this liquid has an extraordinary effect in increasing the action of the file upon the glass, and at the same time protecting the steel instrument from wear. Advantageous as cracks are in glass vessels whenever we wish to separate them into two parts, they are by no means desirable under other circumstances; and it is as important to know how to stop their progress, as to lead them forward. This is readily done in stout glass, by drilling a hole about half an inch in advance of the crack, which gradually passes on into it, and then its further progress is arrested. Holes may be drilled in glass with a common drill and bow, the place being first marked with a file or flint, and the drill point kept wet with oil of turpentine. (It is hardly necessary to state, that a crack existing in the neck of a decanter, and liable to be forced apart with the stopper, could not be arrested in its progress by such means.) If necessary, a little emery powder may be used with the oil of turpentine; and after the operation, the hole must be filled up with some cement; if the vessel is to be used for holding liquids, a little fresh slaked lime, moistened with equal parts of white of egg and water, may be used for this purpose.