Tiiffcrenl Kimh of Coal for the purpose of Illuminalion. 30 



nutes 30 seconds. The pressure by water-gauge at the bur- 

 ner was To ths of an inch. 



From 1 ton of coal, about 8000 cubic feet of gas are obtained. 



The gases obtained with my experimental apparatus, from 

 a variety of samples of the same kind of coal, both lately, 

 and several years ago, were very nearly of the same compo- 

 sition. Different heats were used in driving off the gas, with 

 the view of finding the best heat. The condensation by chlo- 

 rine varied from 3-5 to 55 ; the average of the trials, amount- 

 ing to eight, was nearly 5, The durability varied fi'om 

 47' 20" to 53' 30" ; the average being 50' 25". 



The average specific gravity of eight diifei'ent gases was 

 464, the highest being 512, the lowest 414. 



As above mentioned, I take the gas from this kind of coal 

 for illuminating power and durability, and, consequently, for 

 value, as my standard of comparison. 



English Cannel-Coal Gas. — The gas obtained from this kind 

 of coal, such as that from Wigan in Lancashire, with which 

 Liverpool, Salford, and other places are supplied, and that 

 from coals found in different parts of Yorkshire, which are 

 occasionally used at Manchester, are very nearly of the same 

 quality. 



The Yorkshire Parrot Coal, in its appearance and quality, 

 is altogether different from the English caking coal. It 

 more nearly resembles the parrot coal of Scotland. The con- 

 densation by chlorine was 7*66 ; the dui-ability, 52' 30" ; pres- 

 sure at burner, xo- -A. ton of coals yields about 11,500 feet. 



I have already stated, that the chlorine test, with English 

 caking-coal gas indicated 4-33, that with the Yorkshire can- 

 nel-coal gas being 7"66 ; consequently, the illuminating power 

 is as 1 to 1-76. The durabilities being 50' 30", and 52' 30", 

 they are as 1 to 1"03 ; both taken together, makes the value 

 of the latter, for the purpose of illumination, 1'81 to the for- 

 mer, as 1-(1 : 1-76 :: 1-03 : 1-81). 



Wigan Cannel-Coal Gas. — I have had several opportunities 

 of testing the quality of gas from this kind of coal, as at 

 Liverpool, Salford, &c., at which the gas was found to be of 

 the same quality. The chlorine indicated 755. The dura- 

 bility was 57'; the pressure at the burner, x^ths and Troths, 



