1874.] Economy of Fuel. 67 
in which they originate, and will not wear out with it. 
They are the result of numberless observations, and will be 
immutable and eternal like the facts that have been 
observed and the fundamental powers which these facts 
force us to admit.” 
Vil. ECONOMY -OF FUEL: 
By FREDERICK CHARLES DANVERS, Assoc. Inst. C.E. 
has, within the last few years, attracted the attention 
of several of our learned societies, and it is one which 
cannot fail to grow in importance rather than diminish. 
Practically speaking, coal is the only fuel upon which we 
can with any certainty rely for our great manufacturing 
industries; and although this may, in some measure, be 
supplemented by a more extensive use of peat than has 
hitherto been the case, still coal must continue to be looked 
upon as the great staple upon which the chief of our manu- 
factures must continue to depend. Coal, as we have shown 
upon several former occasions, exists only to a limited ex- 
tent, and our existing resources of that fuel are not capable 
of being reproduced, as is the case with wood, and to some 
extent also with peat; and, in order to make our coal 
supply keep pace with the ever increasing demand upon it, 
one of the most important considerations now is, how so to 
economise its use in all branches of manufacture and for 
steam and domestic purposes as to minimise the amount of 
waste which at the present time takes place in the use of it. 
With the view, therefore, of pointing out what may be done 
in that direction, we purpose now to consider how far 
scientific and mechanical improvements have already suc- 
ceeded in that direction, and to what extent further economies 
may be possible. 
Each pound of coal possesses a certain number of heat 
units, and to produce any given results from its combustion 
requires the development of a given number of heat units; 
when, therefore, we find that in order to produce such results 
a considerable number of heat units are expended in excess 
of the theoretical requirements, it is very evident that a 
certain amount of avoidable waste is taking place. It is 
not to be expected that the full economic value of coal can 
ever be attained in most cases, for were such the case it 
_would necessarily follow that the escaping volumes from 
ae important question of fuel economy is one which 
