EXCAVATING MACHINERY USED IN LAND DRAINAGE. iG 
Interest on investment. 
Liability insurance and other insurance. 
Overhead expenses. 
Contractor’s profit. 
THE FLOATING DIPPER DREDGE. 
The floating dipper dredge is probably the oldest and most widely 
used type of machine for the excavation of drainage ditches. The 
essential parts are: Hull, engines, boiler, A frame, swinging circle, 
spuds, boom, and dipper. With the exception of the dipper, these 
parts appear in some form on every type of steam-operated floating 
dredge used for ditching. Various manufacturers have different 
patented details of construction, but the general principles of con- 
struction and operation are the same for all floating dipper dredges. 
THE HULL. 
The hull may be either of wood or of steel. Use of the latter ma- 
terial will undoubtedly increase in the future, owing to the increas- 
ing cost of suitable timber. Certain fixed relations exist between 
the dimensions of the hull and the positions and weights of the other 
parts of the dredge. The smaller dredged ditches are generally con- 
structed by machines with from three-fourths to 14-yard dippers. 
The machinery necessary for operating these sizes being light, the 
hulls are of such dimensions that they can be floated in smal] chan- 
nels, although the width of hull used for a machine of given capacity 
varies somewhat with different manufacturers. Some bank-spud 
dredges are so designed that the thrust of the dipper when digging 
is carried directly from the A frame through the spud arm to the 
spud shoe and the bank of the ditch. By this arrangement a slightly 
narrower hull can be used. The hulls of vertical-spud dredges are 
wider than those of bank-spud dredges. 
A dipper dredge to withstand the severe stresses due to constantly 
changing loads must be very strongly built. If the hull is of wood 
it is made up of a strong framework of timbers planked on the sides 
and bottom with 3-inch by 12-inch or heavier planking. It is always 
strengthened with numerous cross-trusses inside to tie the boat to- 
gether and prevent crosswise buckling and to insure a stable and 
rigid foundation for the boiler and engines. The hull is strength- 
ened lengthwise by cables which are secured to each end of the boat 
and run over posts placed near the center of each side of the hull. 
A rake of from 4 to 6 inches is given the boat before it is launched, 
the ends being made higher than the middle, so that when the ma- 
chinery is placed on the ends the hull will not be distorted. The 
