REGULARITY UE HEAT AND ECONOMY OF FUEL. 
447 
(cct state at a low temperature, and thus producing volumes of thick 
smoke, which, when once formed, it becomes impossible to burn, 
except at a temperature that will melt iron, which is stated to he 
3000 degrees, and this of course would require an amazing quantity 
of fuel. In Witty’s Patent Gas Furnace, a certain proportion, say 
about a third only, of the floor consists of a grate, («) between which 
and the feeder, ( b) an inclined plane is placed, (c) at an angle of 
30 or 40 degrees: instead of the common door or doors, a sufficient 
orifice is well fitted by an iron box, (d) the part of which, nearest 
the fire, is left open in the form of a hopper*or feeder, to receive the 
charge of fuel.—A flap is closed upon the fuel, and it is pushed forward 
on the inclined plane by a smaller box, or square piston (e), fitted 
within the hinder part of the large box, moved bv a screw, by which 
it is brought back to its first position when a fresh supply is required. 
An arch of brickwork (f) covered by the best non-conductors of heat, 
such, as powdered charcoal, or sawdust, &c. surmounts the plane, and 
leads to the flue, to the bottom of the boiler, or to the body to be 
54 
the fire, are inflamed and completely consumed. This process con- 
