by means of the apparatus described below, and that some glass-workers find it advantageous to use such automatic blowers. But after a little practice, the effort of working the blower with the foot whilst manipulating the glass is not a source of serious inconvenience. Indeed, as it gives a certain degree of control over the flame without the use of the hands, the foot-blower is preferable. It is worth while to describe an automatic blower, however.

Automatic Blower (Fig. 2).—A strong glass tube A is welded into a somewhat larger tube B so that its end is about 2 mm. from the contraction at G. B has a side tube C joined to it. The narrow end of B is fixed by an india-rubber cork to a strong bottle D of two or three litres capacity. The india-rubber cork also carries an exit tube E, and D is pierced near its bottom by a small hole at F.

In using the apparatus A is connected with the water-supply, and water passing through G, carries air with it into D. The water escapes from D by the opening at F, and the air is allowed to pass out by the tube E, its passage being regulated by a tap. Fresh supplies of air enter B by C.

Fig. 3.

Blow-pipe Flames—The Pointed Flame.—If the gas tap of a Herapath blow-pipe be adjusted so that comparatively little gas can pass, and if the foot-blower be then worked cautiously, a long tongue of flame ending in a fine point will be produced (Fig. 3). This flame will subsequently be described as the pointed flame. It should be quite free from luminosity, and as the amount of air necessary for securing a pointed flame is large, in proportion to the gas, there is excess of oxygen towards the end C. By adjusting the proportions of air and gas, pointed flames of various dimensions can be obtained with the same blow-pipe. The part of a pointed flame to be used in glass-working is the tip, or in some cases the space slightly beyond the tip.

Fig. 4.

The Brush Flame.—If a large supply of gas be turned on and a considerable blast of air sent into the flame, a non-luminous flame of great size will be obtained (Fig. 4). In form it somewhat resembles a large camel’s hair pencil, and may conveniently be described as a brush flame. The chief advantage of a large-sized blow-pipe is, that with it a large brush flame may be produced, which is often invaluable. By gradually diminishing the supply of gas and air smaller brush flames may be produced.

The jet used to supply air to the Herapath blow-pipe is usually too fine, and consequently does not permit the passage of sufficient air to produce a brush flame that contains excess of oxygen, even with the aid of a very powerful blower. My own Herapath blow-pipe only gives a satisfactory oxidising brush flame when the jet is removed altogether from the end of the air-tube. For producing pointed flames the finer jet of the air-tube must be used, but when a highly oxidising flame of large size is required it must be removed. The internal diameter of the central air-tube should be nearly half as great as that of the outer or gas-supply tube. Fletcher’s Automaton with the large air jet gives a very liberal supply of air, and produces an excellent oxidising brush flame. In the case of the larger-sized Automaton a consequence of this is, however, that when fitted with the large jet it will not give so good a pointed flame as the Herapath, which, in its turn, gives an inferior oxidising brush. By fitting finer jets to the air-tube of Fletcher’s apparatus pointed flames can be secured when necessary.

The Smoky Flame.—By turning on a very free supply of gas, and only enough air to give an outward direction to the burning gas, a smoky flame, chiefly useful for annealing and for some simple operations on lead glass, is produced.

The Gimmingham blow-pipe and Fletcher’s combination blow-pipe, in addition to the above flames, are also adapted to produce a non-luminous flame, resembling that of the Bunsen gas-burner, which is very convenient for the preliminary heating of the glass, and also for gradually cooling finished apparatus. It is not necessary to describe the method of using these last-mentioned blow-pipes. With the more complicated of them directions for its use are supplied.

Mr. Madan has suggested the use of oxygen in place of air for producing the oxidising flame required for working lead glass, and to produce a flame of high temperature for softening tubes of hard, or combustion, glass. For the latter purpose the employment of oxygen may be adopted with great advantage. For working lead glass, however, it is quite unnecessary if the directions already given are followed.

The student’s subsequent success will so largely depend upon his acquaintance with the resources of his blow-pipe, and on the facility with which he can take advantage of them, that no pains should be spared in the effort to become expert in its management as soon as possible. A few experiments should now be made, therefore, upon the adjustment of the flame, until the student is able to produce and modify any form of flame with promptness and certainty.

Fig. 5.

The remaining apparatus used in glass-working consists of triangular and other files, charcoal pastils for cutting glass, pieces of sound charcoal of various diameters with conical ends; it is convenient to have one end somewhat less pointed than the other (Fig. 5). Corks of various sizes; the smallest, which are most frequently needed, should be carefully cut with sharpened cork borers from larger corks. Besides these there should be provided some freshly distilled turpentine in which camphor has been dissolved,[1] fine and coarse emery powder, and some sheets of cotton-wadding, an india-rubber blowing-bottle, glass tubes, a little white enamel, and a pair of iron tongs.

[1]Half an ounce of camphor to about six ounces of turpentine will do very well.