MECHANICAL VALUE OF COAL. 91 



In conclusion, the author would note that these four methods, 

 considered together, show that the problem of ])ituminous coal com- 

 bustion is receiving its modern solution by the admission of air for- 

 ward or above the grate ; under control as to the amount delivered, 

 to suit the needs of such an ever varying fuel as crude soft coal 

 proves to be. 



Thus, instead of combustion lieing confined to the fire-grate, or 

 being a factoi- of grate surface, or style or proportion of grate (as 

 implied in many patented and peddled nostrums for so-called " smoke- 

 burning ") a most effective vise can be made of solid mineral fuel, as 

 shown by Mr. Crarapton, without any grate, or, as established by 

 Mr. Siemens, if gaseous fuel is used, with the only grate required 

 miles away from the combustion chamber. 



It is now clearly recognized that coal is not a simple substance to 

 be treated in a simple manner, and capable of but one or two com- 

 l)iiiations with oxygen, but that the air needed for its complete com- 

 Inistion is to be supplied in the ever \arying proportions respectively 

 demanded when hydrogen, the various hydro-carbons, carbonic oxide, 

 and fixed carbon (coke) are being burnt ; and that the air must be 

 supplied at the different localities in the furnace or combustion 

 chamber, where these products of the raw fuel are most eftectively 

 oxidized, and, other things being equal, the warmer the air supplied 

 and the less in quantity it exceeds the minimum amount required, 

 and the more freedom given for the flame to burn out free of all con- 

 tact with solids, the higher will be the resultant industrial economy, 

 and the less shall we be troubled with the smoke nuisance. 



A brief discussion followed, in which Mr, Alan Macdougall 

 made some remarks on the value of such knowledge from a 

 sanitary point of view, as the incomplete combustion of coal 

 as shown by the cloud of smoke that hangs over some of our 

 towns, did not add to the public health. 



The President, after expressing his interest in the subject, 

 asked on what the statement was based that hydrogen and 

 carbon combined as in coal seemed to have a higher calorific 

 power than when uncombined. 



In reply to Mr. Macdougall, Mr. Barnett pointed out how 

 much easier it was to avoid smoke and soot from stationary 



