502 



FUKL 



Besides petroleum, several other analogous materials have been proposed as sub- 

 stitutes for coal ; for instance, the oil obtained by distilling particular kinds of coal, 

 or the shale which occurs in coal formations, and more recently the oil known as 

 ' dead oil,' which is one of the products obtained in rectifying the coal-tar of gas 

 works. All these materials resemble each other closely in being composed chiefly of 

 carbon and hydrogen, which are, in various proportions, the combustible and heat- 

 producing constituents of all kinds of fuel. For the application of these materials 

 and of liquid fuel generally, various methods have been proposed. It is desirable to 

 consider in the first place, what is the evaporative power of these materials respec- 

 tively, since that is a very important point to determine in regard to the question as to 

 the relative merits of these different kinds of fuel. 



The following table gives several examples of the total evaporative powers 

 of some kinds of fuel, as calculated from their chemical composition : 



The first line refers to charcoal ; tho second to coke of average quality ; tho third 

 and fourth lines give two examples of hydrocarbons, which comprise between them tho 

 chief ingredients of rock-oil. Lines 5, 6, and 7 give a few examples of coal. They 

 differ from the kinds of fuel previously mentioned, in having some oxygen in tin-in, 

 which somewhat lessens the evaporative power. Here, too, the units of evaporation 

 due to carbon and to hydrogen an; distinguished ; for example, line 6 shows liij units 

 of evaporation due to carbon, and 2;,' dun to hydrogen. Then follow some results tor 

 peat and for wood, on which we need not enlarge. In the third, fourth, ami lilth 

 columns are stated the proportions of the chemical constituents, ranging for the rock- 

 oils, between 84 per cent, of carbon to 16 of hydrogen, and 86 per cent, of carbon to 



