DIRECTIONS FOE USING GAS FURNACES.
The following directions arc given by the manufacturers for working these fur naces: A large unobstructed supply pipe gas is unobtainable, the furnace may be worked at a lower heat by partially closing the top of the chimney until the flame becomes visible, or by working without the chimney. Should the burner plate become red hot, the gas supply is deficient. The points of blue flame should be visible on looking sideways into the burner. To light the burner, insert a lighted taper through the burner easing, up between the grooves in the burner plate, and slowly turn on the gas. On no account turn the gas on before applying and tap must be used, so that the greatest pressure possible may be obtained. The actual amount of gas consumed is, how ever, small. The rubber tubing must be absolutely smooth inside ; tubing made on wire will not work the burners satisfac torily, even if the wire is taken out.
Muffle furnaces of this pattern are sent out with a 2-ft. 6-in. chimney, having a short handle for lifting and a cast-iron foot to steady it. A height of 6 or 9 in. is, however, quite sufficient for photo ceramic work, so that the chimney may be cut shorter. A definite gas supply is specified with each furnace, and this is necessary for working the latter at full power. The flame should be visible in the chimney. Where the full supply of the taper, or a severe explosion may result. If the furnace is hot, and it is required to relight it, it may be necessary to cover the air opening round the gas entrance, to prevent the flame descending through the gauze at the moment of light ing. The burners must be kept clean, for which purpose they are made to take apart.