part 4.J Hughes : Subsidiary materials for artificial fuel. 1G1 
The principal qualities to be aimed at or avoided in the substances used are;—■ 
1st.—- To supply any defect in the combustibility of the raw material. 
2nd. —To prevent the fuel from crumbling in the fire. 
3 r d .—Not to augment the quantity of inorganic matter in the mass. 
Tar and, above all, pitch are the matters best adapted to fulfil all these conditions. 
The principal substances proposed, or that have been the subject of experiments, are as 
follows:— 
1st. —Vegetable and mineral tars, fluid and dry pitch, asphalt, bitumen, resin, and 
gutta-percha. 
2nd. —Amylaceous substances, damaged starch and farinaceous matter, residues 
from the manufacture of starch, &c. 
3rd. —Fatty matter, animal or vegetable, oil-cake (colza, poppy, &c.). 
1th. —Gelatinous matter, gelatine, glue, debris of horns, dung, &c. 
5th. —Mucilaginous matter, certain decomposed mosses, &c. 
6th. —Potash or soda soaps. 
7th. —Oxygenous substances, such as nitrate of soda, chlorate of potash, and 
peroxide of manganese. 
8th. —Earthy plastic substances, clay, plaster, lime, tarry cement, and silicate of 
soda. 
Inorganic substances. —The inorganic matters comprised under the two last headings 
are evidently only applicable for the manufacture of fuel for domestic purposes, where the 
object is to sustain combustion for a long time without letting the heat be too strong. 
M. Habets leaves it to be inferred that the oxygenous substances are added to modify in this' 
case the purely deadening iniluenco of the incombustible earths, which form as much as 
25 per cent, of the compound. 
Amylaceous substances. —After tar and pitch, starchy matters are those which have 
been most frequently used. In fuel for domestic consumption they have replaced tar, on 
account of the inconvenience arising from the odour of the latter material. With a proper 
draught, however, no annoyance at all is felt. 
Tar. —Tar, which is still employed to a certain extent in England, has almost entirely 
fallen into disuse in Belgium, and is only retained in a few French factories, it having been 
found that bricks made with tar will not bear long carriage, that they stick together when 
placed in heaps, and that they give off in burning a great deal of smoke and a disagreeable 
smell. 
Fluid pitch. —The manufacture with fluid pitch, which in 1858 had made rapid progress, 
is now (1871) only carried on in two factories in Belgium, namely, at Sauwartan—where 
Knab’s system of coking furnishes the necessary pitch—and at Gosselics, where the em¬ 
ployment of Evrard's machinery necessitates its use. The plant required for the application 
of fluid pitch is much larger and more difficult to keep in repair than that required for dry 
pitch. Heaters, pumps, tubes, mixing screws, and special distributers, &c.,must be provided; 
skilled workmen must be employed, and the drawback arising from imperfect distillation 
in the drying process must be guarded against, otherwise the bricks will be too smoky and 
melt in the sun. 
Dry pitch. —Dry pitch has almost universally superseded fluid pitch, for experience has 
shown that less machinery is required to work it with, a more regular product is obtained, 
and the bricks are less liable to soften. Its employment permits a certain degree of auto¬ 
matism, which has had the most happy result in the lowering of the cost, owing to the 
