183 
lastly, by being burnt in long galleries, it forms large de- 
posits of a most excellent lamp black. The residue, (pitch,) 
when cold, is ground, and mixed with small coal in the 
proportion of 1 to 4, and having been again heated, is cast 
into brick-shaped moulds, and subjected to an enormous 
pressure. The composition of one of these bricks was 
carbon 76.60, hydrogen 5.15, nitrogen 1.54, oxygen 9.63, 
ashes 7.08, in 100 parts; while another specimen more 
accurately analysed gave from 79 to 80 per cent, of carbon, 
and from 4 to 5 of ashes. 
These patent fuels have many great advantages, and some 
qualities equally prejudicial. Their form, that of equal- 
sized cubical bricks, renders them well adapted for stowage ; 
for although the specific gravity of patent fuel is' lower 
than that of ordinary coal, from their shape and mechanical 
structure, there are few coals which could be stowed away in 
a smaller space per ton. When examined in the Admiralty 
coal investigation, the three patent fuels of Warlich, Wylam, 
and Bell, ranked among the highest result obtained, and in 
the order named. For the purpose of the steam navy, how- 
ever, the dense black smoke they evolve during combustion 
is extremely inconvenient, betraying, as it does, the position 
of ships of war at a time when it is most important to pre- 
serve concealment. This, added to the fact that the bitumen 
they contain renders them liable to spontaneous combustion 
in hot climates, has hitherto prevented their meeting with 
the notice they deserve. Errors in their manufacture are 
frequent, as the mixture of bituminous or tarry matter with 
bituminous coal, instead of with anthracitic, as theory would 
point out ; and in some varieties the addition of large quan- 
tities of lime, salt, clay, and other incombustible matters, has 
occasioned the production of so great an amount of ash as 
to prevent their application to any economic purpose. 
Having, then, discussed briefly the nature of the different 
