In order to drill a hole in glass, it is necessary to have a hard and well«tempered steel drill. This may be prepared by heating to a dull red, and then plunging into mercury so as to become hard. It is, however, necessary to temper the shaft of the drill. Imbed the point of the drill in a piece of lead. The temperature of the shaft of the drill can be raised by means of a blow-pipe till there is a blue colour nearly to the point. The drill and lead together are now immersed in cold water, when the first will be ready for work. This tool, when mounted in a holder and with.the point moistened with turpentine, attacks glass rapidly. Do not press too heavily when working the drill, and, if possible, work from both sides of the glass successively. To enlarge a hole thus obtained, use a rat-tailed file soaked in turpentine. A steel drill may be hardened, when at a red heat, by dipping it into any cool liquid. Another method is to saturate commercial muriatic acid with zinc - do this in the open air. The drill should be ground before hardening. When at a red heat, dip it in the solution to harden; or a spear-shaped drill, heated to a red heat and hardened in mercury, and then sharpened on an oilstone, may be used.

Still another method is to forge a drill at a low temperature and harden it in water. The drill is firmly rotated at the desired spot with an alternate motion, and lubricated with a saturated solution of camphor and spirit of turpentine. Dilute sulphuric acid may also be used as a lubricant. A very simple tool for boring glass is a drill made by heating an old three-cornered file, which is then cooled slowly in ashes. The end is filed to a conical shape and again heated, and then hardened by plunging into water. The drill is fixed in a brace and rotated, turpentine being used as a lubricant. To remove the drill from the hole, rotate the drill in the reverse way. A reliable method of drilling holes, in which a tube is used, is as follows. Make a drill from brass tube of the required diameter, and into the non-cutting end drive a piece of wire to project somewhat, and file the projecting part to fit a drill-stock. The cutting end of the brass tube is next to be slotted with a few saw-cuts running parallel with the tube's length; the inner ends of the cuts must terminate in holes drilled, before the slots are cut, at right angles to the tube's length. The number of slots required depends upon the diameter of the tube used.

Two pieces of wood, measuring, say, 3in. wide, J in. thick, and long enough to spau the piece of glass, are screwed firmly together with ordinary wood screws passing through near the ends, whilst through both pieces of wood a hole is bored large enough to admit the drill freely. This hole through the wood is to be countersunk at both ends. The two pieces of wood are next separated, by partly removing the screws, and the glass is placed between them to be held as in a kind of clamp, the hole for the drill being brought exactly over the spot where the glass is to be bored. Some 90 or 120 grade emery powder mixed with water is then placed in the countersinking to act as a grinding agent. The drill may be worked as fast as possible, though -not so quickly as to splash out the wet emery. When the drill is half-way through the glass from one side, a hole should be started from the other side and completed, to prevent the chipping of the edges. Holes from 1/8in. to 2 in. diameter can be bored with this appliance.

It takes about four minutes by this method to drill holes up to 1/2 in. diameter in a sheet of glass 1/8 in. thick.

To cut a 1-in. hole in a glass plate a copper tube may be used for drilling. Use a tube about 7/8 in. diameter with the end spread to l in. diameter. Emery powder should be fed inside the tube to form the cutting material and turpentine used to dissipate the heat. The tube must, of course, be pressed on the glass and rotated.