EXCAMBION 



Excambion. ' Term used in 

 Scots law for an exchange of lands. 

 The law allows this to be done in 

 the case of entailed property, as 

 well as unentailed, several statutes 

 to this effect having been passed. 

 It is often done to make boundaries 

 and the like more convenient. 



Excavation. In engineering, 

 term used for the removal of ma- 

 terial for building and other pur- 

 poses. In nearly every branch of 

 engineering excavation work oc- 

 curs, from the sinking of a well to 

 the construction of huge reservoirs, 

 ship canals, railway tunnels, etc., 



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several tons each, and work on a 

 face 12-16 ft. high. This machine, 

 usually self-propelling, has in front 

 a swivelling jib made up of two 

 powerful girders, between which 

 swings the back end of a beam. 



To the forward end of the 

 beam is attached a large steel 

 scoop, holding up to five cubic 

 yards of material, and provided 

 with a flap bottom that can be 

 tripped by pulling on a cord. The 

 mechanism includes gear for re- 

 volving the jib ; racking the beam 

 inwards or outwards to vary the 

 reach of the shovel : and lifting the 



involving the use of tools from the 

 simple pick and shovel to giant 

 excavators (q.v.), dredges, etc. 



Excavation problems are among 

 the most difficult the engineer has 

 to solve, the mere task of removing 

 the material being a simple one 

 compared with the difficulty of 

 preventing the sides of the excava- 

 tion from collapsing. The excava- 

 tion of the Panama Canal (q.v.), in- 

 volving the removal of 175,000,000 

 cubic yards of material, was con- 

 siderably delayed for this cause. 

 The original plans were altered 

 because the soft earth could not be 

 prevented from spreading. Great 

 masses of earth, constituting the 

 adjoining banks in the deepest 

 parts of the Culebra Cut, slid down 

 into the canal, necessitating con- 

 stant dredging to restore naviga- 

 tion. Excavating is an important 

 part of archaeological work. See 

 Archaeology ; Canal ; Dredging ; 

 Foundation ; Tunnel ; also illus. 

 pp. 811 and 813. 



Excavator (Lat. ex, from, out; 

 cavare, to hollow). Mechanism 

 for removing large masses of 

 earth. Some of the digging ma- 

 chines used closely resemble the 

 various kinds of dredgers. The 

 spoon dredger has its counter- 

 part in the steam-shovel or 

 steam-navvy, which will deal with 

 anything from soft earth to 

 lumps of blasted rock weighing 



EXCAVATOR 



shovel by means of a chain or cable 

 passing over the end of the jib. In 

 operation the scoop is lowered to 

 about rail level, and thrust forward 

 while being lifted. At the end of 

 the stroke, the jib is swung to 

 bring the scoop over a dirt car, and 

 the contents are dumped by re- 

 leasing the bottom. 



In the hands of skilful operators 

 a shovel will pick up and deliver 

 four loads per minute. A ninety- 

 ton machine, controlled by three 

 men, can move 3,600 tons a day, 

 performing the work of 2,000 hand 

 labourers. An immense amount 

 of excavation was done on the 

 Panama Canal works by these giant 

 diggers in combination with me- 

 chanical unloaders which enabled 

 ten men to clear in a day as much 

 as would have kept 500 men busy 

 with shovels. The steam-navvy is 

 found very valuable for purposes 

 other than those of civil engineer- 

 ing, being widely used for stripping 

 the useless " overburden " of sur- 

 face deposits of coal and iron ore, 

 digging ore and phosphates, and 

 excavating dry gold-bearing gravel 

 in " placer " mines. 



Another excavator, used chiefly 

 for earth and gravel, is the 

 French navvy, which moves on 

 rails along the top edge of the cut, 

 drawing the spoil towards it in an 

 endless chain of buckets running 

 round a sheave at the end of a jib- 

 supported ladder. The buckets ex- 

 cavate while travelling upwards 

 under the ladder, and the spoil is 

 discharged into a shoot, or on to a 

 belt-conveyer for delivery to cars, 

 or directly on to a dump. As ex- 

 cavation proceeds, the ladder is 

 lowered gradually till the full depth 

 commanded by the machine is 

 reached. The excavator then lifts 



Excavator. Crane navvies on mountings suitable for various types of work. 

 1. With caterpillar travelling gear. 2. On road wheels. 3. Mounted on rail wheels 



By courtesy of Rutlon & Horn&by, Ltd. 



