ON CONSUMPTION OF FUEL AND PREVENTION OP SMOKE. 109 



Table of Results, 



Selected from thirty Experiments obtained by Mr. Houldsworth's Pyrometer, 

 indicating the mean temperature of the flues in a steam-engine boiler, and 

 the effects produced by the admission of air through regulated and perma- 

 nent apparatus behind the bridge. 



By comparing the results as given above, it will be found that in taking 

 the quantity of water evaporated by 1 lb. of coal as the measure of oeconoraic 

 value, the mean of nearly the whole experiments (excepting only Nos. 12, 

 13 and 28, where air is not admitted) is as 100 to 112-65, or about 12^ 

 per cent, in favour of a regulated and continuous supply of air. Taking, 

 however, the mean of experiments, 25 to 29, and comparing it with some of 

 the others, it will be observed that a much higher duty is obtained j and 

 having accomplished a maximum, there appears no reason for doubting why 

 it should not be continued, and still further advantages secured by a judicious 

 arrangement of the furnace for the admission of oxygen to the uninflamed 

 gases, which under other circumstances would make their escape into the 

 atmosphere unconsumed. In furnishing this supply it is not absolutely ne- 

 cessary to administer it immediately behind the bridge, as the same quantity 

 of air taken through the grate-bars, or in at the furnace-doors, would nearly 

 effect the same purpose, not only as regards the quantity of heat evolved, 

 but also as respects the transparency of the gases and the consequent dis- 

 appearance of smoke. 



Mr. Houldsworth estimates the advantages gained by the admission of 

 air (when properly regulated) at 35 per cent., and when passed through a 

 fixed aperture of 43 square inches, at 34< per cent. This is a near approxi- 

 mation to the mean of five experiments, which, according to the preceding 

 table, gives SSi per cent., which probably approaches as near the maximum 

 as can be expected under all the changes and vicissitudes which take place 

 in general practice. 



On a cursory view of the subject, it is obvious that the quantity of air ne- 

 cessary to be admitted will greatly depend upon the nature and quality of 

 the fuel used. In a light burning fuel, such as splint and cannel coal, less 

 air will be required, as the charge burns freely with clear spaces between the 

 grate-bars, and attended by less risk of cementation than the caking coal, 

 which in some cases completely seals the openings, and thus deprives the 

 fuel of that quantity of air necessary for its combustion; under such circum- 

 stances a permanent opening will be found exceedingly efficacious, and that 



