The *C" burner with by-pass is shown in Fig. 657. The feature of this burner is a lever arrangement, either with or without chains, which, on being turned up after opening the gas-tap, allows the burner to be lighted as would be the ordinary "C" burner, but if the gas-tap is left open, and the lever of the by-pass turned down, then the bunsen flame is extinguished, but at the same time a small jet is kept burning inside the mantle. By this arrangement the relighting of the bunsen burner can be effected by simply raising the by-pass lever again. It is a very simple arrangement, and strongly recommended.

Great care should be taken with burners of this kind, as the small brass tube inside the bunsen burner must always be kept in its proper position. By taking off the gallery from the bunsen tube, it will be seen that inside it is a small brass tube. When the gallery is replaced, care must be taken that the lighting-back plate stands with its curved edge upwards, and that the three bottom brass points of the gallery come right down on to it. The object of this is to ensure that the little tube enters the socket inside the gallery. If the tube does not enter the socket, then the by-pass will not work properly, and the gas will bubble on the gauze of the bunsen burner, make an unpleasant noise, and create an objectionable smell by escaping. Every burner is manufactured so that this small tube fits exactly into the inner hole of the by-pass; but sometimes it gets knocked out of its position, and then it must be bent so that it fits correctly again into the hole referred to, in the inside brass top of the gallery.

Fig. 657  Welsbach Incandescent C  Burner with By pass.

Fig. 657- Welsbach. Incandescent "C"- Burner with By-pass.

By the employment of the by-pass burner a great economy in the use of gas may be obtained, as people using it would soon get into the habit of turning down the gas when it is not required, feeling that there would be no trouble in relighting it when necessary. The by-pass jet consumes about 2 cubic feet of gas in 24 hours, so the consumption of gas need not be taken into account, as, if it burned for the whole year with gas at 3s. per thousand, it would not consume more than about 2s. worth. In bedrooms the by-pass jet answers the purpose of a night-light, as it gives just sufficient light to mark its position but not more.

The "C" burner with by-pass and governor, is the ordinary "C" burner with the additions of by-pass tap and governor as described above.

The "S" burner with by-pass is made on the same principle as the "C" burner with by-pass. It gives approximately only 30 to 35 candles, and for house-purposes this is often quite sufficient This burner is regulated to consume 2 cubic feet of gas per hour, at 1 inch pressure. In comparison with an ordinary Bray burner, it consumes only one-half the quantity of gas, whilst giving double the amount of light, one-half the quantity of heat, and one-half the quantity of carbonic acid.

As the quantity of heat given off by all burners (including the incandescent)

Fig. 658. Three  light Incandescent Ventilating Lamp.

Fig. 658.-Three- light Incandescent Ventilating Lamp.

Is the same per cubic foot of gas consumed, the incandescent (consuming as it does only one-half the amount required by a No. 5 Bray burner) will only give off half the amount of heat, and will therefore be less efficient when used for the purpose of extracting air for ventilation. Where there are clusters of incandescent lights, however, the total amount of heat given off will be a valuable aid to ventilation, as the up-currents through the chimneys will carry the whole of the heat and carbonic acid away through the flues provided, as well as induce a current of air from the apartment. Two ventilating lamps are shown in figs. 658 and 659; the smaller (Fig. 658) carries away the products of combustion from the burners, and ventilates the room by withdrawing air at the level of the ceiling. In the larger lamp (Fig. 659) there are no openings at the ceiling-level; the air must enter from beneath the glass shade, making it impassible to thoroughly change the air in a moderate-sized room. All the heat and products of combustion pass away through the casing to the flue provided above the fitting.

The principle adopted is the same as in the "Wenham" lamp, as both lamps draw the supply of air (necessary for the complete combustion of the gas passing through the burners) from the apartment, and pass it away, by means of an inside tube, to the flue above. Both kinds of lamps are also adapted to induce a current of air to pass through the perforations at the ceiling-level, in the direction of and through the same flue as the heated air and products of combustion. The "Wenham" lamp is much superior to the incandescent for the purpose of creating and maintaining a current of air in one direction from the apartment, owing to the consumption of gas, and the heat given off being greater. Provision must also be made for a larger volume of air to pass through the casings of the "Wenham", thus ensuring a more rapid and thorough ventilation of the apartment.

Fig. 659  Large Incandescent Ventilating Lamp.

Fig. 659 -Large Incandescent Ventilating Lamp.

With most ventilating lamps, reflectors of various shapes and materials - for fixing internally or externally and sometimes both - are required to reflect the light down wards, owing to the lights themselves being kept as near as possible to the ceilings. Opal reflectors do not darken the ceilings above them so much as metal or silvered glass reflectors, and are therefore much better. It is not customary to use reflectors with other classes of house-fittings, except in the case of billiard-table lights and reading-lamps, and with both these fittings the cardboard shades are used more to protect the eyesight, owing to the flame being much lower than when used for ordinary lighting purposes. Such shades are usually green outside and white inside, the white acting as a reflector, but not to the same extent as the materials usually employed. Silvered copper and glass are the best reflectors, but both appear to be fast dying out, porcelain-enamelled iron being now used when subjected to great heat, and opal glass in other cases.

The burners used for oil-gas are ordinary "Brays", but instead of using Nos. 3, 4, or 5 as with coal-gas, burners numbered 0000, 000, 00 are required. Although these sizes appear very small in comparison with the ordinary coal-gas burners, they will be found to give a light at least equal to the coal-gas burners, owing to the greater illuminating power of the oil-gas. It is also found that this gas gives better results than coal-gas, when it is consumed in the Welsbach incandescent burners.