28 BULLETIN 300, U. S. DEPARTMENT OF AGRICULTURE. 
of the laterals, and the latter are too small and too short to warrant 
installation of a separate machine. The laterals are usually con- 
structed after the main canal has been completed, so that a dam must 
be built in the main ditch to hold the water at the desired elevation 
when constructing the laterals. Where topography and other con- 
ditions permit, a better plan would be a supplementary ditch parallel 
to the main channel, with short laterals of such length as not to re- 
quire dams to maintain the water level. With such a layout the sup- 
plementary canal and laterals may be constructed by one dredge much 
cheaper than if each lateral had an outlet into the main ditch. The 
topography of the ground would determine the feasibility of this 
plan and the length of the laterals. The water should be at such 
height, if practicable, that not over 2 feet of face is exposed. 
THE FLOATING GRAB-BUCKET DREDGE. 
The floating grab-bucket dredge differs from the dipper type in the 
apphances for handling the material and in the operating machinery. 
Instead of using a dipper and dipper handle, an orange-peel or a 
clam-shell bucket is suspended from the end of the boom. The bucket 
of orange-peel type is generally used for drainage work, as it operates 
more satisfactorily in stumpy ground and on materials of varying 
density. 
The floating grab-bucket dredge may be of the gravity-return or 
of the bull-wheel-swing type, and it can be operated by a single engine 
of uniform speed. Hoisting and swinging are accomplished by drums 
operated by friction clutches. In Plate II, Figure 1, a typical orange- 
peel dredge is shown. 
A much longer boom can be used with the grab-bucket dredge than 
with the dipper dredge. From 75 to 90 feet is about the maximum 
length of boom that can be successfully operated on a dipper dredge, 
while booms as long as 240 feet, operating. 6-yard buckets, have been 
used on grab-bucket dredges. This feature is of especial importance 
in levee construction, where it is desired to deposit the material as far 
from the stream as possible. 
While the dipper dredge puils itself ahead by means of the dipper, 
some kind of pull-ahead line is necessary with a grab-bucket dredge. © 
Generally three auxiliary drums are provided, two for operating the 
spuds and one for drawing the pull-ahead line which is secured to 
the bucket. The bucket is dropped into the material, the hoisting 
line is slackened, and the pull-ahead line is drawn taut, pulling the 
dredge ahead. In other cases the pull-ahead line may be anchored to 
a deadman buried some distance ahead of the machine. 
For depositing at some distance from the edge of the ditch ma- 
terial excavated by floating grab-bucket dredges equipped with short 
