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On the Pi-evention of Smoke and Economy of Fuel by the use 

 of Steam^ in the Patent Process of Ivison. By Andrew 

 Fyfe, M.D., F.R.S.E., F.R.S.S.A. Communicated by the 

 Royal Scottish Society of Arts.* 



In the papers on the Evaporative Power of Coal which I 

 have already laid before the Society, I ventured to throw out 

 the conjecture, tliat it depends on the proportion of fixed car- 

 bon which it contains, independent of the volatile inflammable 

 matter ; that, in fact, the greater the proportion of this ingre- 

 dient, the greater would be the amount of available heat 

 evolved during the combustion ; and that I am correct in this 

 opinion is still further confirmed by what was stated in the 

 paper submitted to the Society on the 28th ult. 



Thus, in the trials recorded in the first paper, with coal 

 which contained 50.5 per cent, of fixed carbon, the practical 

 evaporative power was 6.2. According to the fixed carbon, 

 it ought to have been 6.2. In another trial in which the per- 

 centage of fixed carbon was 6.7, the evaporation amounted to 

 7.8, it ought to have been 8.0 ; and in a third it was 8.73, in- 

 stead of 8.78. In the paper lately read to the Society, the 

 result of trials with a different coal were given ; it was 5.8 ; 

 according to the proportion of fixed carbon, it should have 

 been 6.1. 



From these results I think that I am warranted in draw- 

 ing the conclusion, that the practical evaporative power of a 

 coal is just as the proportion of fixed carbon ; that is, as the 

 quantity of carbon which the coke from the coal contains. It 

 is evident, however, that this remark applies only to bitumi- 

 nous coal, or to anthracite of inferior quality, and which, 

 from its containing volatile inflammable matter, resembles 

 other kinds of coal ; for when a fuel is composed almost entirely 

 of carbon, as is the case with the best anthracite, were it ex- 

 l)ected that the practical evaporative power would be equal to 

 the amount of fixed carbon, which is occasionally 94 per cent., 

 then this fuel would drive off' nearly as much water in vapour 



* Read before the Royal Scottish Society of Arts, 25tU April 1842. 



