PERFORATING GLASS, EAurtiEri wenn, &c. The only tools requisite for this are a few worn out three-edged hand-saw files. These being generally made of cast steel, retain when ground a very fine point, which is of the utmost importance. In order, however, to give them the requisite degree of hardness, it is necessary to make their ends, for about an inch, red hot, and then plunge them into cold water. By this treatment they become hard and brittle ; care is, therefore, required in grinding them to a proper point, which is easily effected on a common grindstone. There generally is given to them a few rubs on a fine oil-stone after the grinding, so as to produce a very finepoint. A cylindrical piece of any sort of wood, about two inches long, terminated by a half-round end, having a hole about the tenth of an inch in di ameter, through its axis, may either be fastened into a common bench vioe, or on a table. This constitutes the only support required. Suppose that a glass to cover the face of a wheel barometer is wanted, through which it is sometimes necessary to make a perforation for the purpose of passing the screw of the non?' ious through • a proper piece of gills.; being selected, is to be marked with a dot of ink on the place where the intend ed perforation is to be made ; the glass is then to he held horizontally by the left band, and immediately over the hole in the wood support above men tioned. A three-edged file having been hardened and ground to a fine point in the manner above described, is held firmly between the fore-finger and thumb of the right hand, precisely in the posi tion that a pen or pencil is retained when writing. The pointed steel is then to be repeatedly impinged against the glass over the spot intended to be perforated, taking care not to use too much violence. In a short time the outer surface is re moved, and, by a continuation of the pro cess, a conical piece is forced from the under surface of the glass through a hole in the wood support ; the perfora tion so produced never exceeds in size a pin's head, but may be made as large as required by holding it over the hole in the support, and working round its edge with a fine pointed file. In this way,
after a little practice, and in a very few minutes may be perforated, with ease, all descriptions of glass, from the thin nest crown to the thickest plate, without any danger.
Wine-glasses or tumblers may, also, be easily perforated in a similar manner; but there is mostly employed another process for them. These being made of a softer sort of glass, require only to be moved by the hand backwards and forwards, in the manner of drilling, on the sharp point of the file, with the occasional as sistance of a little oil and emery. In deed any sort of glass may be perforated in this manner, but not so quickly as by the method of punching. All the varie ties of china and earthenware may be perforated by either of the above pro cesses with certainty.
PERFUMERY.—Dr. Ure in his Diction ary of the Arts, gives the following di rections for obtaining and preparing the most important essences, &c., which are slightly condensed. The essential oils or essences obtained in the south of France are those of roses, neroli, petit-grain, lavender, wild-thyme, thyme, and rose mary. These essences are distilled in the usual manner. They obtain, by put ting into the body of the still 40 lbs. of rose leaves, and 80 pints of water, and pr,ceeding to distillation, 15 pints of rose-water. They then continue the operation until they have obtained 200 pints of water, termed No. 1. In this first distillation, they obtain an almost imperceptible quantity of the essence of roses ; but in the second it becomes more apparent ; and, finally, in the fifth it be comes notable.
In the distillation of orange-flowers, they also obtain the essence of neroli, now become of remarkable importance. If they would obtain this essence they fol low the ordinary process, and repass the waters of the first distillations upon new flowers. On the contrary, when it is in tended to prepare orange-flower water of a good quality, they draw off a fifth part only of the water placed in the cucurbit.