EXCAVATING MACHINERY USED IN LAND DRAINAGE. 3 
In late years the so-called dry-land excavators of various types have 
been developed and have reduced the cost of excavation under con- 
ditions to which floating dredges are not adapted. The growth of 
the drag-line scraper excavator has been especially prominent. At 
present this machine probably has a wider field of usefulness than any 
other type of excavator made. 
The cost of all kinds of excavation has now reached a very low 
figure as compared to the prices prevailing for work by machinery 
only a few years ago. This has mainly been brought about by the 
entrance into the contracting field of many men equipped with 
modern machinery who, through the keen competition, have taken 
contracts at prices permitting only a small margin of 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 the hull, engines, boiler, A-frame, swinging circle, 
spuds, boom, and dipper. With the exception of the dipper theseparts 
appear in some form on every type of floating dredge used for ditching. 
Various manufacturers have different patented details of construction, 
but the general principles of construction and operation are the same 
on all floating dipper dredges. 
ESSENTIAL FEATURES OF CONSTRUCTION. 
HULL. 
The hull may be either of wood or of steel; the use of the latter 
material will undoubtedly constantly increase in the future owing to 
the ever-increasing cost of timber that is suitable for building hulls. 
The many difficulties met with in the operation of the earlier machines 
have taught manufacturers that certain fixed relations exist between 
the dimensions of the hull and the positions and weights of the other 
parts of the dredge. Unless these relations are considered in the 
design of the hull much trouble will result in the operation of the 
dredge. The smaller dredged ditches are generally constructed by 
machines with from 1 to H yard dippers. The machinery necessary 
for operating these sizes being comparatively light, the hulls are 
of such dimensions that they can easily be floated in the smaller 
channels, although the width of hull used for a machine of given 
capacity varies somewhat with the different manufacturers. Some 
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 than is necessary where the machine is 
differently designed. 
