The ordinary Bray's burner is the one in most general use. It is in no sense a governor, although it is arranged to check the pressure, and requires to be selected according to the amount of light required, and the pressure of the gas-supply. Only a governor-burner can be fixed without regard to the pressure of the supply, and as the "Bray" is not a governor, a selection must be made. Three kinds are shown in section in Fig. 649. The commonest form a has a canvas screen fixed inside the body, and the "special" burner has an enamel plug in addition to the canvas screen. The hole through the enamel plug is graduated to suit the various pressures, and the holes or slits in the burner heads. To get the full amount of illumination obtainable, the size of the burner must be decided upon after testing the various sizes. No. 3 and No. 4 union-jet burners give good results in most cases. All the "specials" are good when selected to suit the varying requirements in each particular case.

The consumption of gas with any particular size of burner will vary with the pressure as well as the quality of the gas supplied. This also applies to the candle-power of all burners; the tabulated results of tests, giving illuminating power, consumption, and pressure, are of little value, except as showing the varying efficiencies at the particular time and place of testing. The quality of the gas supplied, as well as the pressure, varies so much that it would be unfair to select any series of tests and use them to decide the relative merits of the various burners. To set down the tabulated results of tests made for the rival manufacturers of gas appliances would be very misleading, as in most cases such tests are made at the pressure most suitable for the particular burner. In a test

Gas Burners 50096Gas Burners 50097Fig. 649.   Sections of three Bray's Gas burners

Fig. 649. - Sections of three Bray's Gas-burners.

A, burner with union jets; B. special slit union burner: c, standard slit-union burner (made in sixes from SO to SO candle-power) made to ascertain the effect of increased pressure upon the quantity of gas consumed, it was found that, with a small burner at two-tenths pressure, there was a consumption of 1890 cubic feet per hour; and, increasing the pressure by tenths, it was found that, at ten-tenths, there was a consumption of 4.800 cubic feet per hour, the average increase of consumption for every tenth of pressure being 0.3 cubic feet per hour. Here the quality of the gas and the illuminating power of the burner are neglected, but it will be seen that the consumption of gas increases or decreases according to the pressure. In order to compare fairly the tests of rival burners, it is necessary to know not only the pressure and the consumption of pas in cubic feet per hour, as well as the candle-power, but also the quality of the gas. The standard illuminating power of the gas supplied in the various cities and towns varies considerably, and, besides this, there is always a slight variation in quality even in the same locality.

The albo-carbon burner was designed to achieve the carburation of coal-gas by the admixture of hydro-carbon vapour. It consists of a receptacle or generator for the "albo-carbon", this material being vaporized and mixed with the gas before the flame is reached It is claimed that, by using an 8-light albo-carbon cluster of the kind suitable for shop windows, the lighting power is over 8 standard candles for every cubic foot of gas burned, as against 3 candles per cubic foot when gas is burned in the ordinary way. To charge the generator, unscrew the rap of the feeding-screw provided, and fill the vessel with pieces of the albo-carbon, taking care not to injure the screw, and also to properly screw up the cap to prevent leakage When the gas is first lighted, the albo-carbon in the iterator will be solid, and some few minutes must elapse before the heat from the flame is sufficient to volatilize it. and thus cause it to issue from the burners with the coal-gas, which is thoroughly carburetted by the admixture of the hydro-carbon vapour. Care must l>e taken not to move or shake the generator whilst warm, as the albo-carbon is then in a liquid state, and will block up the tubes and burners. It is a cheap and effective system, well recognized and appreciated by the public, who have adopted it where a brilliant and steady illuminant is required at a moderate cost, but it is somewhat dirty in use.

Argand burners are a great improvement on the ordinary burner, and give a steady light of considerable power. They were first invented by Aime Argand, who was born at Geneva in 1755, and were of course designed for oil-lamps. The principle has since been successfully applied to gas-burners. It consists essentially of an annular cylinder; the gas enters the annular space and escapes through a series of small holes in the upper edge of the cylinder, forming a circular flame, to which the air has access on both sides. A chimney is necessary to create a draught and steady the flame, and to obtain the greatest illumination. A section of Sugg's argand burner is shown in Fig. 650, which, although a little more complicated, answers to the foregoing description.

Regenerative gas-burners, which are all more or less indebted to Siemens's original patent, now form a very important class of fittings, the central idea being to raise the air and gas to a high tern perature (by means of the products of combus-tion) on their way to the actual burner.

Fig. 650.   Section of Sngg's Argand Burner.

Fig. 650. - Section of Sngg's Argand Burner.