part 4.] Hughes: Subsidiary materials for artificial fuel. 163 
The fuel so prepared was tried at the mint, but it burnt in a dull, smouldering manner, 
gave a bad welding-beat, and loft a groat deal of clinker. An assay proved it to contain 
102 per cent, of water and 22'6 per cent, of ash—an amount of useless matter that could 
not fail to retard oombustion. 
As a highly oxygenous substance, it might have been supposed that the addition of 
nitrate of soda would assist combustion, but any advantage that the presence of this salt 
ought theoretically to confer would be neutralised by the heat lost in evaporating the water 
that it absorbs readily from the atmosphere. Four grains arc scarcely an appreciable 
quantity, and would yield only enough oxygen to enter into combination with less than one 
grain of carbon. To be of any theoretical value, it must bo used in larger proportion than 
that given above. But tho use of nitrate of soda is, I think, questionable, on the ground of 
its deliquescent nature, unless a plan of rendering each lump of fuel thoroughly water¬ 
proof can be adopted. It must also affect the formation of clinker. 
Gum, which is one of the ingredients, has never been brought into practical use in 
Europe owing to its price, and the same circumstance will probably militate against its 
employment in this country. 
When a farinaceous cement is employed, it is usual to add some alum in order to 
strengthen it. The Diamond Fuel Company, which is now working Barker’s process, use 
sulphate of alumina or chloride of alumina in hydro-chloric acid, in the proportion of one 
ounce to a gallon of solution of starch. Tar, or bettor still pitch in small proportion, is also 
added in a small proportion to render tho fuel less friable and more water-proof. In the 
case of the Warora fuel, neither alum nor pitch was used. 
The Darjiling dust coals approach in composition those of anthracitic regions, and will 
require a cement that does not consume in the fire more rapidily than tho coal, for it has 
been found that “if tho agglutinating material burns too briskly, the particles of coal 
having lost their adhesive coating crumble in the fire and fall through the grate unconsumed.’’* 
Some slow-burning farinaceous cement will probably be the best substance. On the subject 
of Darjiling coal, however, I refer the reader to the detailed report of Mr. Mallet, iu the 
Memoirs of the Geological Survey, Yol. XI, which is now in the press. 
Attempts have been made to coke mixtures of anthracite and bituminous coal-dust, but 
tho coke produced could not bear handling ; it had no density, and it was very porous, owing 
to the fact that the particles of anthracite would not unite with the bituminous particles. 
Putting clay aside as an agglutinating material for tho reason which has already been 
given, the most easily procurable cement in this country is that coming under the head of 
starch; but tar or its derivatives possess properties which render them almost a necessary 
ingredient in most artificial fuels. 
There is not a large native supply of pitch, but tho Bengal Coal Company are carrying 
out experiments in a most spirited way to prove the yields of tar, pitch, oils, &c., from their 
different coals; and the results will give useful data by which to estimate the capability of 
Indian coals as a source of supply. 
Calcutta, 1st October 1874. 
* The “ Journal of the Frankliu Institute,” 1871, Vol, LXVII, p. 118, 
