Makch 25, 1904.] 



SCIENCE. 



489 



ney. If, however, the burning gas becomes 

 cMlled by contact with the relatively cool 

 bricks of the chimney back or if insufficient 

 air is supplied, the yellow flame becomes 

 red and dingy, while particles of finely 

 divided carbon are deposited on the ad- 

 jacent surfaces or whirled away up the 

 chimney. 



The ordinary coal-oil lamp is one of the 

 best illustrations of perfect combustion and 

 consequent smoke prevention. The heated 

 gases rising in the chimney produce a draft, 

 and fresh air is continually drawn in at 

 the bottom through the hot gauze, which 

 warms and divides it so as to insure thor- 

 ough mixing with the gases from the burn- 

 ing oil. Turn up the wick and the flame 

 becomes smoky — too much hydrocarbon for 

 the air supply. Raise the chimney slightly 

 from the bottom and again there is smoke 

 — too much air at too low a temperature, 

 which chills the flame. Insert a cool metal 

 rod into the chimney and soot is deposited 

 on it— chilling of the flame again and dis- 

 engagement of the carbon, while the hydro- 

 gen continues to burn. 



And thus we may learn of the three 

 requisites for good combustion ; enough air, 

 a sustained high temperature and a thor- 

 ough mixing of the gases. The last two 

 are so important that it is entirely possible 

 to have an excessive supply of air and 

 dense black smoke at the same time. 



Having thus decided upon the conditions 

 which promote good combustion and pre- 

 vent smoke, it remains to determine how 

 they may be realized in practise. 



It may be said at the outset that it is 

 entirely possible for a good fireman with 

 his shovel, a pile of soft coal and an or- 

 dinary flat grate, to so fire a furnace as to 

 make practically no smoke. It may also 

 be said that this is highly improbable and 

 that such a man would command higher 

 wages than are usually paid to firemen. 



The best method of hand firing consists 



in first maintaining as uniform a rate of 

 combustion as possible by putting on coal 

 often and in small quantities ; and secondly 

 by varying the air supply to suit any lack 

 of uniformity which may exist. This is 

 known as the one-shovel system of firing 

 and has been successfully used on many of 

 the leading railroads as a means of saving 

 coal and reducing smoke. The nation 

 which shortens its swords lengthens its 

 boundaries and the railroad which shortens 

 its coal-scoops lengthens its mileage per 

 ton. The air supply is usually varied by 

 leaving the door slightly ajar just after 

 coal is put on and then closing it when the 

 coal begins to glow. Several automatic ap- 

 pliances for doing this have been invented 

 and in numerous instances have given good 

 results. The iisiial plan is to have the de- 

 vice operated by the opening of the fire 

 door at the time of firing. 



When the door is opened some simple 

 combination of levers and chains raises the 

 piston of a dash-pot, which in turn lifts a 

 flap in the door itself and opens the valve 

 in a steam-pipe connecting with a system 

 of steam- jets over the door. After the 

 door is closed the flap in the door remains 

 open and so do the steam-jets. The draft 

 created by the latter assists to draw in ad- 

 ditional air and the steam mixes it thor- 

 oughly with the burning gases. The jets 

 should be directed to the back of the flre 

 near the bridge wall. All this time the 

 plunger of the dash-pot is slowly settling 

 down, dropping the air damper and closing 

 the steam-valve until at the instant when 

 the fresh coal becomes incandescent the air 

 supply is shut off. If the apparatus is 

 made to operate a check-draft in the uptake 

 at the same time the efficiency will be still 

 more improved. 



The efficiency of such an arrangement 

 can be clearly represented by diagrams, 

 one showing a cloud of black smoke just as 

 it is cut off by the apparatus being thrown 



