EXCAVATING MACHINERY USED IN LAND DRAINAGE. 5) 
the greater convenience and labor saving through its use are to offset 
the increased cost of equipment. The selection is usually confined 
to steam and internal-combustion engines, because the work generally 
takes place out of reach of electric transmission lines. 
STEAM ENGINES. 
The determination of the economical fuel to use for a steam plant 
requires a knowledge of the heating qualities of fuels and of their 
costs delivered at the machine. Of the fuels wood, coal, and oil, wood 
has the lowest heat value. The range in heating units is not as great 
in wood as it is in coal, because the ash and moisture contents of 
coal vary considerably. It is advisable to purchase coal containing as 
little ash as possible. Oils have a considerably greater heat value 
than either wood or coal. Some of them, such as Mexican oil, have 
a higher heating value than others, but are difficult to use on account 
of their greater viscosity. : 
The following is a comparison + between bituminous coal and crude 
oil from Beaumont, Tex., containing 19,060 British thermal units 
per pound: 
Comparative evaporative power of oil and coal. 
1. Pounds of evaporation per pound of coal with about 10 square feet of 
Neat Me sikidce-per DOMer NOrsSepOWweris =. a (63) 
2. Pounds of evaporation per pound of Beaumont oil with about 10 square 
feet of heating surface per boiler horsepower_______________-__-__.___ 14.8 
Pe eaOemieeVAOraLion Of Ol-tO COdl_. = 8 ee OT: 
4. Number of barrels of oil equivalent to a ton of coal________________ = __ 3. 04 
The coal used was measured by the gross ton of 2,240 pounds. It 
contained 3 per cent of water and was representative of the bitumi- 
nous coal obtained from mines west of Ohio in the Central Western 
States. The oil weighed 7.66 pounds per gallon, or 322 pounds per 
barrel of 42 United States gallons. The figures give net evaporation 
after allowing for steam consumed to produce the forced draft 
necessary for burning the fuel. 
Authorities generally estimate that 24 pounds of dry wood are 
equivalent in evaporative power to 1 pound of good bituminous coal, 
or 0.6 pound of average fuel oil. The American Society of Mechani- 
cal Engineers has adopted for tests the’ ratio of 1 pound of wood to 
0.40 pound of coal. Solid bituminous coal weighs approximately 84 
pounds per cubic foot, while loosely broken bituminous coal weighs 
49 pounds per cubic foot. Assuming a cord of wood to weigh 2,000 
pounds, 24 cords are equivalent to 1 short ton of coal. In construct- 
ing channels in heavily timbered sections where the right of way 
1 Denton, Prof. James E. Power, February, 1902, p. 8. 
