246 A TREATISE ON DREDGES AND DREDGING 



the water is liable to do damage to nearby property. At times 

 centrifugal pumps are used to excavate foundation pits and coffer- 

 dams. Such pumps are mounted on platforms or skids, and are, 

 as a rule, of a smaller size than those used on dredges. 



Grapple dredges are used quite extensively for dry-land work. 

 Both clamshell and orange peel buckets are used on these machines. 

 In some cases the hoisting machinery is simply mounted on a moving 

 platform or skids or gunwales and the bucket is operated on a 

 derrick. The whole machine is moved either on rollers or wheels, 

 and is operated by a crew of three or four men. Even sewer trenches 

 are excavated with such an apparatus, and besides the various kinds 

 of work previously mentioned, railroad embankments and levees 

 are sometimes built with such a land dredge. On extensive work 

 such machines are often worked in pairs. Such dredges can work 

 in hard as well as soft materials, and will work both in dry and wet 

 excavation. These buckets are also used in foundation work, to 

 excavate inside of coffer-dams. 



Grapple dredges mounted on scows are also used on dry-land 

 work, but not as extensively as dipper dredges. When there is no 

 water to float them at first, a pit is dug and water pumped or turned 

 into it. Both are used in a manner similar for such dredges in rivers, 

 except in canals and ditches that are but little wider than the scow, 

 the spuds are outrigged in a manner somewhat like the jack arms 

 of a steam shovel, and are held in place on the banks of the ditch. 

 Such spuds are called "bank spuds." 



Dipper dredges used for such work vary in size from dippers 

 of 1 cu.yd. or less up to 10 or 12 cu.yds. As a rule the excavated 

 material is deposited on the two banks. 



Another type of bucket used for dry-land work is shown in 

 Fig. 81. These are used on long derrick booms, and in some cases 

 by means of a deadman set ahead of the machine material beyond 

 the reach of the boom is excavated. Such buckets are in nearly all 

 cases patented. The best known are the Page, the Channon, the 

 Heyward, the Browning, the Austin and the McCormick. Some- 

 times the derricks are mounted on scows and then used as a dredge 

 for ditch or canal excavation. Locomotive cranes are also used 

 to operate these buckets, as well as orange peel and clamshell 

 buckets. Some manufacturers also rig them to tuko a dipper arm 

 and steam-shovel dipper, but when so equipped they are classed 

 with steam shovels. 



