EXCAVATING MACHINERY USED IN LAND DRAINAGE. 33 



machine making two 4^-foot cuts side by side. The average length 

 of ditch cut per day was 800 feet, while the maximum was 1,950 feet. 

 The daily cost of operation was as follows: 



Labor $5. 50 



Fuel 4.20 



Incidentals 50 



Repairs 2. 40 



12.60 



The average excavation per day was 410 cubic yards, based on the 

 average of 800 feet of ditch, 4J feet deep, 4J feet wide at the top, and 

 20 inches wide at the bottom. The machine excavated 82,330 cubic 

 yards in 18 months at the following itemized cost: 



Gasoline based on 215 actual days' operation (estimated) $903. 00 



Repairs, actual cost 860. 00 



Incidentals, at 50 cents per day 120. 25 



Labor of foreman, 1 8 months, at $75 per month 1, 350. 00 



Other labor, two men, $2.50 per day for 250 days 625. 00 



Interest and depreciation 2, 675. 25 



Total 6, 533. 50 



Cost per cubic yard, $0.0793. 



THE HYDRAULIC DREDGE. 



The hydraulic dredge has little application in the construction of 

 ditches for drainage purposes, due to the fact that nearly all the drain- 

 age ditches are of too small a cross section to be economically dug by 

 this method. This type of dredge probably is, however, the most 

 economical machine existing for excavating very large channels. 



The essential parts of the hydraulic dredge are a centrifugal pump 

 and the power to drive it, the whole mounted on a barge. The 

 suction pipe is attached to the pump by a movable joint so that the 

 suction end can be raised or lowered. The material, mixed with 

 water, is drawn through the suction pipe and discharged where 

 desired through a line of pipe sometimes several thousand feet long. 

 Coarse sand and gravel, muck, and silt are easily handled in this way, 

 and by the use of a rotary cutter on the end of the suction pipe, com- 

 paratively hard clay can be removed. The machine does not work 

 well, however, where there are stumps, logs, stones, or other such 

 obstructions. 



Dredges of this type are suitable for digging ditches 800 or more 

 square feet in cross section, for building levees under favorable con- 

 ditions, and especially for building up tidal flats and low lands. 



COST OF OPERATION. 



The following table indicates the cost of operating a hydraulic 

 suction dredge on the New York Barge Canal in 1908. The dredge 

 in question is of modern construction, has a 20-inch discharge pipe, 



