The operation of cutting glass, consists in leading a crack in the required direction; this is readily done by a hot iron rod, a piece of pointed burning charcoal, or, what is still better, a burning pastile—which is somewhat similar in its composition to those used for fumigation; and which latter, although rather expensive, and inconvenient from their shape, may be applied for the purpose. When the operation of cutting up glass vessels into useful forms is much had recourse to, pastiles are prepared for the purpose, being superior to a heated iron rod, as they continue to burn and retain their heat, whilst the latter requires to be re-heated, if the crack has to be led any considerable distance. Pastiles are readily made by rubbing up half an ounce of powdered gum tragacanth with water, so as to form a mucilage about as thick as ordinary starch; this should be allowed to remain a few hours, and then mixed with a quarter of an ounce of benzoin, previously dissolved in the smallest possible quantity of proof spirit; after mixing them together in a mortar, as much powdered charcoal should be added as will form a stiff paste, and the whole well worked together, rolled into sticks the size of a common black-lead pencil, and dried. As thus prepared, they should be free from cracks, and solid throughout; and on being ignited at the end, they will burn steadily away to a point. If an iron rod is used, it should be nearly as stout as the little finger, and taper at the end for an inch and a half to a blunt point. Before commencing the line along which it is wished to divide the glass, it should be marked with a pen and ink, and allowed to dry, when the iron, heated to dull redness, or the lighted extremity of the pastile, should be brought to the end of a crack, being held in a slanting direction with regard to the glass, as shown in the cut, and slowly moved in an oblique direction towards the line; the crack will be found to follow the heated point, and may be thus led as required, even passing over parts varying very considerably in thickness, as in the case of the flutings on a cut decanter; but it cannot, with certainty, be made to pass suddenly from a very thin to a very stout part, or the reverse: thus it may be led around the sides of a tumbler, but could hardly be made to pass down one side, across the bottom, and up the other. The rapidity with which the operation is performed, depends upon the heat of the iron or pastile; if the former is very hot, or the latter made to burn more vividly by blowing upon it, the operation is quickened, but it is not performed with so much certainty, as the crack may pass on further than is desirable: care should be taken not to lead the crack too near the edge of the vessel, or to another crack, as in that case it is apt to leave the proper course, and fly suddenly to the edge, to which an inexperienced operator should not attempt to go nearer than half an inch. [Illustration]