()J A TREATISE ON DREDGES AND DREDGING 



the orange-peel bucket. The bucket of the clamshell dredge is 

 built of different shapes, depending upon the materials that the 

 machine is designed to work upon. Thus, for instance, the bucket is 

 made up of tines when the dredge is to work in a soil full of 

 pebbles or small boulders, or is intended to pick up stones that have 

 been broken up by blasting. A solid bucket with the edges provided 

 with tines is used in connection with dredges intended to work in 

 soils that are hard and compact, while a clamshell bucket without 

 tines is used for working through very loose soils. The orange-peel 

 bucket of the grapple dredge cannot be subdivided, being always 

 of the same shape. Both types of dredges vary greatly in dimension 

 of machines, although they are similar in their chief characteristics. 



It is possible to divide all dredges into two classes, namely, 

 self-propelling or non-propelling. A self-propelling dredge can 

 be moved by its own power, but when not provided with self-pro- 

 pelling apparatus dredges are moved by tugboats, or by chains or 

 moorings. All the sea-going dredges of the ladder and hydraulic 

 type are self-propelling, while many of the same type of dredges 

 as well as those of the dipper and grapple type are usually stationary 

 or non-propelling. 



Self-propelling dredges meant for harbor and river work are 

 also rigged to be moved by hawsers and moorings, or by means of 

 spuds. 



The self-propelling dredges can be provided with motive power 

 -sufficient to move the boat while the dredging operations are 

 going on, or it may be necessary to stop dredging in order to 

 furnish the power for the propelling apparatus. In other words 

 on the same machine the advance of the boat and the dredging 

 operations can be made either simultaneously or alternately. 



As stated, all the sea-going dredges are self-propelling and so 

 are some of the dredges of small dimensions used in the excavation 

 of rivers, canals, etc. The propelling devices vary; for instance, in 

 the sea-going dredges it generally consists of one or two propellers 

 of the same form and dimension as used in steamers of similar 

 capacity. However, paddle-wheels are sometimes used. These 

 ma} 7 " be located on each side of the boat as in any ordinary >i de- 

 wheel boat which plies on the large rivers and bays. Paddle-wheels 

 are not extensively used on dredges, owing to the fact that either 

 the dredging or discharging apparatus is usually located on the 

 sides of the boat. The propelling device may consist also of a si 



