EXCAVATING MACHINERY USED IN LAND DRAINAGE. 13 
THE BOILER. 
The boiler most commonly used on floating dredges is of the loco- 
-motive type, with either open or water bottom. ‘This type is adapted 
to burning the various kinds of fuel. The Scotch marine return-flue 
boiler is the more economical of fuel and is used to some extent. It 
does not burn wood as well as the locomotive type. The ordinary 
working pressure in these boilers ranges from 125 to 150 pounds. 
The capacity of the boiler should be at least 25 per cent greater than 
that theoretically required to operate the engines. Because foul 
water must often’be used, the boiler should have two separate feeds, 
usually an injector and a duplex pump. In addition to these, some 
operators include an inspirator. 
Boiler compounds frequently are used to prevent foaming. Where 
the water is muddy, it can be filtered through hay or gravel in a box 
or barrel through which the feed water is pumped. Clear water 
may sometimes be obtained by extending the intake pipe behind the 
dredge a hundred feet or so, supporting it on barrels or similar floats. 
Manufacturers generally designate boilers by their size instead of 
their horsepower, although users prefer to designate them by the 
horsepower produced. Makers usually consider that 10 square feet 
of outside heating surface covered by water is necessary for each 
horsepower developed. Table 4 gives the sizes of locomotive-type 
boilers ordinarily furnished for the various sizes of floating dipper 
dredges. 
TABLE 4.—Dimensions aid cost of locomotive-type boilers. 
Approxi- 
Capac- Heati | 
: a ; ating | Grate Tat 
ity of Size of boiler. <a Weight. mate 
Bickel. surface. area. o price. 
Cu. yds. : Sq. ft. Sq.ft. | Pounds. 
LL 2" RUSH EYG cYS 6 W'S) i a ny See 410 14.5 10, 200- $2, 275 
is |-o4 inches, by 16leeb 4 inches: 22... 222 -.-2-.<----5-.2.-- 667 21.4 14, 400 3,175 
PERC ITCHeS Dy -Lorect/ Simches: -55- 4. 22205. 2a 808 21.4 155750) eetoecD 
221 601nches by. 20feet 7inches.-!.-..22-2..-.---2:-<.---- 1,147 28.8 21, 800 4,975 
2) bul AEE EE CEES Obl Noes) pe Erbakel ta ee ee el eee BAS coke 
Ae aw OOO Neh eSiD yet feeta.2- 2! 2 ee es Le 1, 886 ZA OS eta SOOO kee eee 
er wooo wuches Dys20 feet 7 mches:\ 2-2 2 e+ | ETAT. ON ee ae Poe eee 
| | 
1 Each. 
ENGINES. 
Floating-dipper dredges are of three types, according to the method 
in which the hoisting rope is reeved; that is, the dipper is operated by 
either a one, two, or three-part cable. With a single-line hoist the 
power of the engines is compounded through gears, whereas with the 
double and triple hitch the power is compounded between the point 
of the boom and the dipper by means of sheaves attached to the 
dipper bail. The speed of the main engines and of the bucket, as 
