LOCOMOTIVE ENGINES.

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contrivances have been tried, and none with better results thanindependent steam jets fitted to the fire box, forcibly inducting airby steam pressure amongst the incandescent fuel. With this objectin view, the front and back or sides of the fire box are fitted with arow of tubes, placed at a convenient height above the fire bars. Asteam pipe is fitted at the front, side, and back of the fire box,having a nozzle connected with each hollow stay or tube, theapertures being T V inch in diameter. A vertical pipe is fitted tothis steam pipe, running to the top of the outside of the fire box,having a plug tap for regulating the supply of the steam. It hasbeen proved by experiment that this contrivance greatly preventssmoke nuisance when coal alone is used, and effects a materialsaving in fuel. A much simpler plan, however, has been success-fully adopted in coal-burning engines fitted with the ordinary firebox: it consists of ä plate, easily removed, fitted to the apertureor fire door, and which is inclined downwards. By this means thecurrent of air entering by the fire-door aperture passes downwards,instead of taking the direct course through the tubes,—thus meetingthe flame and heated gases, and providing the necessary oxygen toefifect complete combustion.

The ordinary fire box of the locomotive-engine boiler has beenmodified in various ways to effect a thorough combustion of thefuel, and likewise to prevent smoke nuisance when coal is used.All of the following schemes depend more or less on a free admis-sion of air, with or without the use of a separate combustion cham-ber, in connection with the ordinary fire box. In land-engineboilers the air is admitted beyond the fuel, through apertures formedin the bridge at the back of the fire bars. Mostly all the mechani-cal contrivances introduced in the locomotive boiler aim at attain-ing the above objects by similar methods, namely, dividing the firebox by means of water spaces, formed of the same material as thefire box, to which latter air is admitted as in the ordinary landboiler.

The first example we will notice has two sets of fire bars laid atan inclination, having over them a hanging bridge, provided withan air pipe at the top. This plan was introduced for burning coalin combination with coke; the large grate was for the coal, andthe small one, or fore grate, for the coke. Coal alone was chargedon the hind grate, and coke on the fore grate, the design being todeflect the flame and heated gases by the hanging bridge over the