Fixtures having too many scrolls or spirals may, in the case of fectly purified gas, accumulate a large amount of a tarry deposit, which, in time, hardens and obstructs the passages. Another fault is the use of very small tubing for the fixtures. Common forms of brackets are shown in Figs. 118 and 119, the latter being a two-swing extension bracket.
There are an endless variety of gasoliers used, depending upon the kind of building, the finish of the room, and the number of lights required. Figs. 120,121, and 122 show common forms for dwelling houses the type shown in Fig. 122 being used for halls and corridors.
Next to the burner, the shape of the globe or shade surrounding the flame affects the illuminating power of the light. In order to obtain the best results, the flow of air to the flame must be steady and uniform. Where the air supply is insufficient, the flame is likely to smoke; on the other hand, too strong a current of air causes the light to flicker and become dim through cooling.
Globes with open ings too small at the bottom, should not be used. Four inches at the bottom should be the smallest opening used for an ordinary size burner.
All glass globes absorb more or less light, the loss varying from 10 per cent for clear glass, to 70 per cent or more for opal, ground, colored, or painted globes. Clear glass is therefore much more economical, although, where softness of light is especially desired, the use of opal or ground globes is made necessary.
Cooking as well as heating by gas is now very common, and there are a great variety of ances for the use of gas in this way. Cooking by gas is not more expensive, and is less troublesome, than by coal, oil, or wood. It is also more healthful, on account of the sence of waste heat, smoke, and dust. A gas range is always ready for use, and is instantly lighted by applying a match to the burner. The fire, when kindled, is at once capable of doing its full work; it is easily regulated, and can be shut off the moment one is through with it, so that, if properly managed, there is no waste as is the case with other fuel. With gas, the kitchen can be kept compar atively cool and comfortable in summer.
Gas stoves are made in all sizes, from the simple form shown in Fig. 123, to the most elaborate range for hotel use. A range for family use, with ovens and water heater, is shown in Fig. 124. Figs. 125 and 126 show the forms of burners used for cooking, the former being a griddle burner, and the latter an oven burner.
A broiler is shown in Fig. 127; the sides are lined with asbestos, and the gas is introduced through a large number of small openings. The asbestos becomes heated, and the effect is about the same as a charcoal fire upon both sides.
Gas as a fuel has not been used to any great extent for the warming of whole buildings, its application being usually confined to the heating of single rooms. Unlike cooking by gas, a gas fire for heating is not so cheap as a coal fire when kept burning constantly. In other ways it is effective and convenient. It is especially adapted to the warming of small apartments and single rooms where heat is wanted only occasionally and for brief periods of time. In the case of bedrooms, bathrooms, or dressing-moms, a gas fire is preferable to other modes of warming, and is fully as economical. It may be used on cold winter days as a supplementary source of heat in houses heated by stoves or by furnaces. Again, a gas fire may be used as a substitute for the regular heating apparatus in a house, in the spring or fall, when the fire in the furnace or boiler has not yet been started. It is often employed as the only means for heating smaller bedrooms, guest moms, and bathrooms, and for temporary heating in summer hotels where fires are required only on occasional cold days. Any con siderable use of gas for heating necessitates the use of evaporators to maintain the normal humidity of the air.
The most common form of heater is that shown in Fig. 128. This is easily carried from room to room, and may be connected with a gas-jet by means of rubber tubing, after removing the tip. The heater is merely a large burner surrounded by a sheet-iron jacket. Another and more powerful gas heater is the radiator, shown in Fig. 129. This is fitted with a flue to conduct the products of combustion into the chimney, as shown in the section, Fig. 130. Each section of the radiator consists of an outer and an inner tube, with the gas flame between the two. This space is connected with the flue, while the air to be heated is drawn up through the inner tube, as shown by the arrows.
Fig. 131 shows an asbestos incandescent grate; and Fig. 132, a gas log of metal or terra-cotta and asbestos, made in imitation of a wood log or heap of logs. The gas issues through small openings in the logs, and gives the appearance of an open wood fire.
Fuel gas or water gas, largely made to supplement failing supplies of natural gas, is used for lighting in the same manner as natural gas. It is, in fact, but an impure commercial hydrogen made by injecting steam into hot coke. The oxygen of the steam combines with the carbon of the coke, and sets free the hydrogen, which is collected in a gasometer, ready for the distributing pipes. The prime use of this and of natural gases is for heating; but, by purifying it and supple menting it with carbon by incorporating with it vapors of petroleum, fuel gas makes rich and quite stable lighting gas.