BOILERS FOR STATIONARY ENGINES.

45

Another plan for consuming the smoke is attained by blowingsuperheated steam through a number of minute apertures placedat the front of the furnace; with high-pressure steam in the boilers;this plan works well, so long as the apparatus remains in goodorder. The steam requires to be dry before it is sprayed into thefurnace in minute jets above the grate. The steam from the boileris made to flow through a coil of pipes placed in the fire-brick bridge,and then passes through a pipe laid across the furnace front, fittedwith nozzles having holes r V inch in diameter; the pipe is fittedwith a plug-valve to regulate the supply to the nozzles, the furnacedoor being provided with a number of air holes, the superheatedsteam is turned on, causing a powerful current of air to pass throughthe fire door, and before mixing with the gases in the furnace isdistributed with the steam jets into minute atoms, and we maysay the mere forcing of the atoms driving the oxygen throughand between the live coal, produces complete combustion, withgreat economy in fuel. This is much better than any plan weknow of, from the fact that fuel will burn with this arrangementthat would be entirely worthless in ordinary furnaces. By the useof the jets of superheated steam all the waste cinders from thesmithy can be utilized, and dross or small coals effectually burned,without the smoke nuisance; but we unhesitatingly give as ouropinion, that unless the attendant sees that the furnace is kept inproper trim, firing with the least quantity of coal, oft times replen-ished, that all the refinements for the prevention of smoke will notattain the desired object, for careful firing is the main secret toarrive at.

SYSTEMS OF TUBING.

The triangulär and square Systems of tubing have certain advan-tages as well as disadvantages. With the former, almost usedexclusively fcr locomotive boilers, a greater number of tubes can begot into less space, the water being honey-combed as it were witha large amount of heating surface. The tubes for locomotive boilersare generally made of composition metal; this is absolutely requiredwhere deposits form from impurities in the water. When iron orsteel tubes are used, the small water spaces, in some instances onlyhalf an inch, soon get choked up, and the steam does not rise freely;and as the arrangement will not allow of much scraping and clean-