EXCAVATING MACHINERY USED IN LAND DRAINAGE. 29 
booms, steel chutes have been used successfully in the reclamation of 
swamp lands in New Zealand. ‘Two chutes, one on each side of the 
hull, are mounted on steel frames. The saturated material is dropped 
into the upper end of either of the chutes, which have slope enough 
for the material to shde down and fall on the ground some distance 
from the edge of the ditch. 
Owing to its long reach, the grab-bucket dredge is often used for 
levee construction. It is not extensively used for the excavation of 
drainage channels, although under certain conditions it can be used 
to greater advantage than can the dipper dredge. It excels in 
handling the muck found on the prairie lands of southern Louisiana 
and in certain other localities. The dipper type, however, is prefer- 
able for digging hard soil or where there are many stumps. 
There are a great many makes of both orange-peel and clam-shell 
buckets. The dimensions and weights for the several makes vary 
somewhat, although these factors differ but little for the machines 
used on drainage work. 
. THE DRAG-LINE SCRAPER EXCAVATOR. 
The drag-line scraper excavator is a dry-land machine that has 
come into prominence only within the last few years. It has made 
feasible the cheap construction of much larger ditches and levees 
than is possible by the use of any other type of machine. 
In the type most commonly used the engine platform, engine house, 
and boom are connected and revolve on a turntable which is secured 
to a lower platform built up of structural-steel sections. This is 
known as the revolving or rotary type and is illustrated in Plates ITI, 
IV, and V. Upon the upper surface of the lower platform is riveted 
the track upon which the swinging circle revolves, and in its center 
is the pivot bearing. The turntable is a steel-frame circle supported 
by several dolley wheels which rest upon the track. The number of 
dolley wheels varies with the different makes as well as with the size 
of machine, a sufficient number being used in each case to insure the 
required bearing for steady operation. The upper platform, which 
is also built up of standard steel sections, is held to the lower platform 
by the central pivot. 
The rotation or swinging of the machine is accomplished by two 
methods. The method almost universally used is the rack-and-pinion 
method. On the lower platform is a circular rack with cut or cast 
steel gears. In Plate III, Figure 1, both the rack and dolley wheels 
are shown. On the upper platforri are the swinging engines which 
drive a pinion, which in turn meshes into the rack (PI. III, Fig. 2) on 
the lower platform. By this mode of rotation the machine can revolve 
any number of times in either direction. 
