DIRECTIONS TO WORKMEN.

139

rotary retort, at a lower temperature, so as to pro-duce only at the rate of thirteen or fourteen thou-sand cubic feet of gas from the chaldron of coal.In the latter case the manufacturer expends coalin order to save his retort, whereas in the formercase he economizes the fuel, as productive of a gainmore than commensurate for the waste of the retort.

When the supply of gas required, happens at any-time to he less than the retort when in action iscapable of furnishing, the fire must then be keptlow, but the retort should never be suffered to ac-quire a lon er temperature, than that of a dull redheat visible by day-light.