THE EXHIBITION OE 1862. 
139 
in operation in manufactures, steam navigation, locomotion, and 
mining. Tire extent of this force, in this country alone, has 
been differently estimated. In 1859 it was nearly as follows: — 
Steam-Engines employed. 
Horses’ Power. 
Nominal. 
Indicated. 
In Muring and Metal Manufactures 
„ Manufactories 
450.000 
1,350,000 
850.000 
1,000,000 
1.350.000 
4.050.000 
2.550.000 
3,000,000 
„ Steam Navigation 
„ Locomotion 
Total 
3,650,000 
10,950,000 
Or about 11,000,000 horses* power, raising* 33,000 lb. one foot 
high in one minute, or equivalent to the enormous force of 
raising 162,053,575 tons one foot high in one minute, or 
1,620,535 tons to the height of 100 feet in the same time. 
This was estimated as the work done per minute three years 
ago; now it has increased to upwards of 12,000,000 horses — - 
which may be taken as the motive force in the British isles 
alone. 
It would be interesting to know the quantity of coal con- 
sumed for the purpose of generating a force equivalent to 
raising the above enormous load of 9,723,214,500 tons one foot 
high in an hour. This, as already stated, would require the 
strength of 11,000,000 horses to accomplish in one hour, and 
this multiplied by five, the average consumption of coal per 
hour per horse-power, gives 24,533 tons, or about 25,000 tons, 
as the rate of consumption per hour for the steam-power of 
Great Britain and Ireland.* 
Steam-Engines are of three classes, — Stationary, Marine, and 
Locomotive; and these are again subdivided into Condensing 
and Non-condensing Engines. Nearly all at the present time 
work the steam expansively ; that is to say, they are so ar- 
ranged in the construction of the valve motions, as to cut off 
the communication with the boiler at one-third, one-half, or 
two-thirds of the stroke, as the case may be, in regard to 
pressure, or the power to overcome the resistance of the load. 
Some engineers go so far as to cut off the steam at one- sixth and 
one-eighth, and expand the remai nin g five-sixths or seven- 
eighths of the stroke. f The expansive system is now thoroughly 
* Vide “ Useful Information for Engineers,” p. 206. 
t The distance which the piston travels is called- the stroke, and is -twice 
the radius of the crank. 
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