MECHANICAL VALUE OF COAL. 83 



Possessing — as peat does — so large a proportion of volatile com- 

 bustible matter, it will in Canada eventually be used by conversion 

 on the spot into gaseous fuel, conveyed through pipes, and consumed 

 where required in some form of regenerative furnace, or exj)loded in 

 the cylinder of a gas-engine. 



Thei-efore, the manufacturer's choice in fuel, this year, is between 

 the two coals — anthracite (hard) and bituminous (soft); and the 

 first question that arises is. What is their relative value as fuels, say 

 for making steam 1 and does the larger percentage of carbon in hard 

 coal justify its current high reputation and the top market price? 



Our answer is no ! certainly not ; and the general opinion (some- 

 times strongly stated), that pound for pound hard coal is the better 

 fuel, is due to a crude comparison of elementary assays, rather than 

 to pi'actical tests carried out under every-day working conditions. 



Analysis shows as high as 94 per cent, of fixed carbon in American 

 hard coal, in comparison with ?(• to 80 percent, of fixed and volatile 

 carbon in soft coal ; and, as the oxidation of this carbon is the main 

 source of all furnace heat, there would seem to be a good basis of fact 

 to support the common opinion. 



Such inference, however, neglects to take into consideration the 

 physical (uiolecular) condition of the coal. 



Heat being vibration, the more dense and compact the atoms of 

 the fuel, the gieater is the percentage of the whole amount expended 

 (commercially wasted) in raising the remainder to that state of free- 

 dom in which it fan swing freely, oi-, in other words, the utilizable 

 calorific value of carbon per unit weight varies inversely as its density. 

 This holds good fur every form of carbon, so that, as for instance in the 

 diamond, the known condition in which molecular compression is 

 greatest, its calorific value is very low. 



Another reason why coal should not be valued and purchased 

 on analysis as we would purchase metallic ore, is, that the law of 

 union under which the various and variable substances forming coal 

 originally united, and now separate — or recombine in distillation on 

 the tire-grate, — is not seen clearly enough to permit of its power 

 being gauged by simple analysis ; and there are experiments that 

 lead to the conclusion that C and H united as in some coals have 

 higher calorific powei's than when uncombined. This is so difficult 

 to conceive — seeing that in combination they possess no apparent 

 explosive power — that Messrs Kestner and Meunier's experiments, 



