74 Economy of Fuel. ‘[January, 
a horse power during five hours thirty-three minutes. 
Practically, however, the results obtained fall very far short 
of these results. An ordinary non-expansive non-con- 
densing engine requires commonly a consumption of from 
to lbs. to 12 Ibs. of coal per horse-power per hour, whereas 
a good expansive and condensing engine accomplishes the 
same amount of work with 2 lbs. of coal per hour. 
In order to attain the greatest economy of fuel, used for the 
purpose of producing mechanical action, it is first necessary 
to provide such an amount of heating surface in the boiler 
as shall absorb all the heat produced by combustion, and 
transmit it to the water. The beneficial results which are 
attained by the greater size of boiler in relation to the coal 
burnt and to the horse-power required have been proved by 
actual usage, and are not merely matters of calculation. The 
Institute of Mechanical Engineers instituted a careful inquiry, 
in 1863, into the consumption bythe best engines in the Atlan- 
tic Steam Service, and the result showed that it fell in no case 
below 43 lbs. per indicated horse-power per hour. Last year 
they assembled with the same object in view in Liverpool, 
and Mr. Bramwell produced a table, showing that the average 
consumption by seventeen good examples of compound 
expansive engines did not exceed 2} lbs. per indicated horse- 
power per hour. Mr. E. A. Cowper has proved a consumption 
not exceeding 1} lbs. per indicated horse-power per hour, ina 
compound marine engine constructed with an intermediate 
superheating vessel in accordance with his plans. Dr. 
Siemens has, however, proved that theoretical perfection 
would only be attained if an indicated horse-power were 
produced with about 41b. of ordinary steam coal per hour. 
Mr. Bramwell, in his address as President of Section G, 
at the meeting of the British Association at Brighton, in 
1872, bore testimony to the fair duty done by locomotive 
engines, which he stated to be due, first, to the fact that, 
since the introduction of coal the furnaces have been to a 
considerable extent gas furnaces, with a free admission of 
air through open fire doors to the surface of the fuel; and, 
secondly, to the fact that the boilers have large absorbing 
powers. In marine engines there has, within the last ten 
years, been an enormous saving. The old fashioned engine, 
working at 20 lb. steam and with injector condensers, is 
being abandoned for engines generally on the compound 
cylinder principle, working at 60 lb. and 70 lb. steam, highly 
expansive, and fitted with surface condensers; and the result 
is a reduction of the consumption of fuel in the same 
vessels, on the same voyages, and performed in the same 
i 
en ce En Ae 
