200 REPORT—1840. 
to the boiler, and the third to the engine. The main constituents of 
coal are carbon and bitumen: the former is convertible, in the solid 
state, to the purpose of generating heat; the latter, in the gaseous 
state alone, and to this latter is referable all that assumes the character 
of flame. The greater part of the practicable ceconomy in the use of 
coal being connected with the combustion of the gases, this division of 
the subject is peculiarly important. Having explained the nature of 
combustion, Mr. Williams went on to show that all depended on bring- 
ing the combustible and the air into contact in the proper quantities, 
of the proper quality, and at the proper time, the proper place, and the 
proper temperature. The conditions requiring attention were, Ist, the 
quantity ; 2nd, the quality of the air admitted ; 3rd, the effecting their 
incorporation or diffusion; 4th, the time required for the diffusion ; 
and 5th, the place in the furnace where this should take place. 
Mr. Williams exhibited several diagrams, representing the several 
processes connected with the combustion of a single atom of coal-gas 
or carburetted hydrogen, and also of bodies or masses of such gas. 
The essential difference between the ordinary combustion of this gas 
in combination with atmospheric air, and that resorted to by Mr. 
Gurney in combination with pure oxygen, in what is called the Bude 
light, was then explained. By these diagrams it was shown, Ist, what 
was the precise quantity of air which the combustion of gas demanded ; 
2nd, the degree or kind of mixture which combustion required ; and 
3rd, that the unavoidable want of time in the furnace to effect this 
degree of diffusion was the main impediment to perfect combustion, 
and the cause of the generation of smoke. 
From the consideration of these details, the inference followed, that 
smoke, once generated in the furnace, cannot be burned—that, in fact, 
smoke thus once generated became a new fuel, demanding all the 
conditions of other fuels. Mr. Williams dwelt much on the chemical 
error of supposing that smoke or gas can be consumed by bringing it 
into contact or connexion with a mass of incandescent fuel on the bars 
of a furnace ; that, in fact, this imaginary point of incandescence, or 
the contact with any combustible body at the temperature of incan- 
descence, was peculiarly to be avoided, instead of being, as hitherto, 
sought for ; and hence the failure of all those efforts to prevent or con- 
sume smoke. The great evil, then, of the present furnaces, was their 
construction, which did not admit the necessary extent of time (or its 
equivalent), time being essential to effect the perfect diffusion of mix- 
ture of the gas. Mr. Williams then proceeded to show, that unless 
some compensating power or means be obtained, and practically and 
ceconomically applied, we can never arrive at full combustion, or prevent 
the formation of smoke. This compensating power was shown to be 
obtainable by means of surface, and was well exemplified in the blow- 
pipe; the remedy, then, for the want of time in the furnaces, may be 
met, by introducing the air in the most effective situation, by means of 
numerous small jets. Mr. Williams submitted the primary law to be 
this, viz. that no larger portions of air, that is, no greater number of 
atoms of air, should be introduced into any one locality than can be 
