lvi REPORT— 1863. 
when these natural falls will be brought into useful operation. In that day 
the heat of the sun, by raising the water to heights from which to flow in 
these great rapids and cascades, will become the means of economizing the 
precious stores of motive power, which the solar energy differently directed 
has accumulated at a remote period of geological history, and which when 
once expended may probably never be replaced. 
T have hitherto spoken of coal only as a source of mechanical power, but 
it is also extensively used for the kindred purpose of relaxing those cohesive 
forces which resist our efforts to give new forms and conditions to solid sub- 
stances. In these applications, which are generally of a metallurgical nature, 
the same wasteful expenditure of fuel is everywhere observable. In an ordi- 
nary furnace employed to fuse or soften any solid substance, it is the excess 
of the heat of combustion over that of the body heated which alone is ren- 
dered available for the purpose intended. The rest of the heat, which in 
many instances constitutes by far the greater proportion of the whole, is 
allowed to escape uselessly into the chimney. The combustion also in common 
furnaces is so imperfect, that clouds of powdered carbon, in the form of smoke, 
envelope our manufacturing towns, and gases, which ought to be completely 
oxygenized in the fire, pass into the air with two-thirds of their heating 
power undeveloped. 
Some remedy for this state of things, we may hope, is at hand, in the gas 
regenerative furnaces recently introduced by Mr. Siemens. In these fur- 
naces the rejected heat is arrested by a so-called “ regenerator,” as in Stirling’s 
air-engine, and is communicated to the new fuel before it enters the furnace. 
The fuel, however, is not solid coal, but gas previously evolved from coal. A 
stream of this gas raised to a high temperature by the rejected heat of com- 
bustion is admitted into the furnace, and there meets a stream of atmospheric 
air also raised to a high temperature by the same agency. In the combina- 
tion which then ensues, the heat evolved by the combustion is superadded 
to the heat previously acquired by the gases. Thus, in addition to the ad- 
vantage of economy, a greater intensity of heat is attained than by the com- 
bustion of unheated fuel. In fact, as the heat evolved in the furnace, or so 
much of it as is not communicated to the bodies exposed to its action, con- 
tinually returns to augment the effect of the new fuel, there appears to be no 
limit to the temperature attainable, except the powers of resistance in the 
materials of which the furnace is composed. 
With regard to smoke, which is at once a waste and a nuisance, having 
myself taken part with Dr, Richardson and Mr. Longridge in a series of ex- 
periments made in this neighbourhood in the years 1857-58 for the purpose 
of testing the practicability of preventing smoke in the combustion of bitu- 
minous coal in steam-engine boilers, I can state with perfect confidence that, 
so far as the raising of steam is concerned, the production of smoke is unne- 
cessary and inexcusable. The experiments to which I refer proved beyond 
a doubt, that by an easy method of firing, combined with a due admission of 
air and a proper arrangement of firegrate, not involving any complexity, the 
emission of smoke might be perfectly avoided, and that the prevention of 
the smoke increased the economic value of the fuel and the evaporative power 
of the boiler. As a rule, there is more smoke evolved from the fires of steam- 
engines than from any others, and it is in these fires that it may be most 
easily prevented. But in the furnaces used for most manufacturing opera- 
tions the prevention of smoke is much more difficult, and will probably not 
be effected until a radical change is made in the system of applying fuel for 
such operations, 
