EXCAVATING MACHINERY USED IN LAND DRAINAGE. 33 
resting on three pontoons. With three pontoons the bearing pressure 
was 1$ pounds per square inch. 
MACHINERY AND EQUIPMENT. 
The power equipment of the drag-line excavator may be either 
steam, gasoline, or electric. On drag-line scraper excavators the 
internal-combustion engine has been used with success. In some 
places the quality of water obtainable for use in boilers and the ab- 
sence of electric power may determine the use of internal-combustion 
engines. 
The machinery for operating the drag-line excavator is placed 
on the upper platform. On excavators operated by internal-com- 
bustion engines the engine may be either gear-connected to the oper- 
ating drum or belt-connected. On steam-operated machines the main 
engines are of the double-cylinder, friction-drum type, mounted on a 
structural-steel base (Pl. VI, Fig. 1). The main engines operate the 
hoisting and loading drums. For rotating the excavators, separate 
engines of the double-cylinder type are used. ‘The boilers may be 
either vertical or locomotive type. ‘Tables 12 and 13 show the dimen- 
sions of engines, boilers, and accessories, average fuel consumption, 
and shipping weights of drag-line excavators of various capacities, 
‘ jroo ‘ 
93127 —22 
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