CHAPTER XVI 

 UNIVERSAL DREDGES 



THE hydraulic dredge was originally designed to work exclusively 

 through very loose soils. It was after some years that, in order 

 to extend the field of its usefulness, devices were applied to disinte- 

 grate the compact soils so as to be taken up by the pump. The 

 hydraulic dredge is a very efficient machine and superior to any 

 other in working through very loose soils, but in hard and compact 

 soils even with powerful cutters these dredges cannot be favorably 

 compared with other machines. In the extensive works of harbor 

 improvement, which, as a rule, extend over a large area, soils of 

 different consistency are encountered. Even if the cutter suc- 

 ceeded in disintegrating the soils, the debris composed of sharp 

 edged broken stones would soon disarrange the pump. Hence in 

 order to obtain the most favorable results under all conditions, it 

 would be necessary to have at hand two different kinds of dredges, 

 one for the loose soils and another for working through hard and 

 compact materials. In such a case only one machine at a time 

 could work, while the second would remain idle. This would involve 

 a very large expenditure, both in the original cost of the larger 

 plant required for the work, and in its running expenses. To avoid 

 this the two different classes of dredging machinery have been 

 mounted on the same hull, resulting in a new machine, called the 

 universal dredge, being a ladder and a hydraulic dredge com- 

 bined. Universal dredges are very powerful machines, built sim- 

 ilar to regular steamers, able to navigate in high seas. They are 

 constructed of two different types, the universal dredge proper 

 and the universal dredge of the hopper type. The former is 

 the one which has on board the two sets of dredging machinery, 

 besides all the machines and conveniences for ocean navigation. 

 The latter is the one that, besides the two sets of dredging machinery 

 and conveniences, has on board a hopper of larger capacity, in 

 which is deposited the debris to be carried away by the same steamer 



and dumped in deep waters. 



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