FUEL 



497 



by a zig-zag horizontal flue or flat pipe d, c, nine inches broad and one deep, ending 

 below in a round pipo at c, which passes through the bottom of the copper bath c,f, 

 and receives there into it the top of a small black-lead furnace b. The innermost 

 crucible contains the fuel. It is surrounded at the distance of one inch by a second 

 crucible, which is enclosed at the same time by the sides of the outermost furnace ; 

 the strata of stagnant air between the crucibles serving to prevent the heat from being 

 dissipated into the atmosphere round the body of the furnace. A pipe a, from a pair 

 of cylinder double bellows, enters the ash-pit of the furnace at one side, and supplies 

 a steady but gentle blast, to carry on the combustion, kindled at first by half an ounce 

 of red-hot charcoal. So completely is the heat which is disengaged by the burning 

 fuel absorbed by the water in the bath, that the air discharged at the top orifice g has 

 usually the same temperature as the atmosphere. 



The vessel is made of copper, weighing 2 Ibs. per square foot ; it is 5 feet long, 1 

 wide, 2 deep, with a bottom 5 feet long, and 1| broad, upon an average. Including 

 the zig-zag tin plate flue, and a rim of wrought iron, it weighs altogether, 85 Ibs. 

 Since the specific heat of copper is to that of water as 94 to 1,000, the specific 

 heat of the vessel is equal to that of 8 Ibs. of water, for which, therefore, the exact 

 correction is made by leaving 8 Ibs. of water out of the 600 or 1,000 Ibs. used in each 

 experiment. 



In the experiments made with former calorimeters of this kind, the combustion was 

 maintained by the current or draft of a chimney open at bottom, which carried off at 

 the top orifice of the flue a variable quantity of heat, very difficult to estimate. 



When the object is to determine the latent heat of steam and other vapours, they 

 may be introduced through a tube into the top orifice g, the latent heat being deduced 

 from the elevation of temperature in the water of the bath, and the volume of vapour 

 expended from the quantity of liquid discharged into a measure glass from the bottom 

 outlet c. In this case, the furnace is of course removed. 



The heating power of the fuel is measured by the number of degrees of temperature 

 which the combustion of one Ib. of it raises 600 or 1,000 Ibs. of water in the bath, 

 the copper substance of the vessel being taken into account. 



It must be borne in mind that a coal which gives off much unburnt carburetted hy- 

 drogen gas does not afford so much heat, since in the production of the gas a great deal 

 of heat is carried off in the latent state. 



The economy of fuel, as exhibited in the celebrated pumping engines of Cornwall, 

 will be dealt with under the proper head. See STEAM ENGINE. And in reference to 

 the ordinary uses of fuel for domestic and other purposes,' see STOVES. 



Prof. T. S. Hunt, in the ' Canadian Naturalist,' July 1861, gives the results of the 

 analyses by various chemists, taken chiefly from Bischof s { Chemical Geology,' show- 

 ing the relative proportions of the elements in wood, peat, coal, asphalte, and 

 petroleum. 



He states that ' the nitrogen, which in most cases was included with the oxygen in 

 the Analysis, has been disregarded, and the oxygen and hydrogen, for the sake of com- 

 parison, have been calculated for twenty-four equivalents of carbon.' 





These analyses are very valuable as showing the variations which the different 

 kinds of fuels exhibit in their passage from vegetable matter to bituminous coal. 

 Vor.. H. K K 



