96 Proceedings of the British Association. 



Gas coals No. 1 Sulphur in 100 parts 3.00 



2 3.90 



3 2.42 



4 3.80 



5 2.50 



6 5.20 



7 3.40 



8 3.50 



Coals lor puddling cast iron to be converted into steel : 



1, hard foliated, or splent, sp. grav. 1.258 .... 0.80 



2, ditto 1.290 .... 0.96 



3, ditto 1.273 .... 3.10 



4, cubical, and rather soft 1.267 .... 0.80 



The presence of much sulphur in a gas coal is a great evil, because it 

 affords, in its decomposition, so much sulphuretted hydrogen, as requires 

 an operose process of washing or purification, which impoverishes the 

 gas, and impairs its iUuminating power by the abstraction of its defiant 

 gas or carburetted hydrogen. Hence I found, in a specimen of coal gas, 

 as generated in the retorts of one of the London gas companies, no less 

 than 18 per cent, of olefiant gas ; but in the same gas, after its purifica- 

 tion from sulphur, I found only 1 1 per cent. With a coal, such as No. 4 

 of the second series given above, at least 10 per cent, of the light might 

 be economized. The apparatus which I employ consists of a large cop- 

 per bath, capable of holding 100 gallons of water : it is traversed, for- 

 wards and backwards, four times, in four different levels, by a zig-zag 

 horizontal flue, or flat pipe, nine inches broad, and one inch deep, end- 

 ing below in a round pipe, which passes through the bottom of the cop- 

 per bath, and receives there into it the top of a small black lead furnace. 

 The interior furnace, which contains the fuel, is surrounded, at the dis- 

 tance of an inch, by another furnace, which case serves to prevent the 

 dissipation of heat into the atmosphere. A pipe, from a pair of double- 

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

 plies a steady current of air to keep up 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 has usually the same tempera- 

 ture as the atmosphere. In the experiments made with former water 

 calorimeters the combustion was maintained by the current of a chimney, 

 open at bottom, which carried off at top a quantity of heat very difficult 

 to estimate. My experiments have been directed hitherto chiefly to a 

 comparison of the heating powers of Welsh anthracite, Llangennech, 

 and a few other coals. I have found, that the anthracite, when burned 

 in a peculiar way, with a certain small admixture of other coals, evolves 

 a quantity of heat at least 35 per cent, greater than the Llangennech 

 does, which latter is reckoned by many to be the best fuel for the pur- 

 poses of steam navigation. One half pound of anthracite, burned with 

 my apparatus, heats 600 pounds of water 10o Fahr., viz. from 62° to 72°, 

 the temperature of the atmosphere being 66° ; so that there is no fallacy 



