SEA-GOING LADDER DREDGES 79 



buckets are all loaded. The dredge is lighted throughout electrically; 

 internally by incandescent lamps, and on deck by arc lamps; current 

 is furnished by a Laval electro-turbine plant. 



With regard to the trials made with this dredge, we cannot do 

 better than reproduce a part of the official reports of the Commis- 

 sion nominated by the Minister of Marine: "The trials provided 

 for by the terms of the contract were carried out on June 18 last, 

 at the same time the machinery was tested for the consumption of 

 fuel. 



"The speed obtained was 6.053 knots; the consumption of fuel 

 contracted for was 2.09 lb., but the tests showed a consumption 

 of 1.97 lb. per horse-power per hour. 



"The trials were continued for six consecutive hours, during 

 which the working was extremely satisfactory. 



" The tests for dredging efficiency were made with material similar 

 to that found in the bed of the Charente; the Commission continued 

 these tests for 60 hours consecutively. 



" It reported that the dredge worked with one engine and one 

 boiler, and that, at the minimum speed of ten buckets per minute, 

 it gave an average efficiency of 485 cu.yds. an hour; this amount 

 included the time necessary for operating the discharge channels, 

 and stopping and starting the machinery; without including these 

 delays, the amount raised was 6536 cu.yds. 



" From the foregoing it will be seen that the efficiency is largely 

 in excess of the terms of the contract, which prescribed a total of 

 333 cu.yds. per hour. 



"The consumption of fuel measured direct under the most unfavor- 

 able conditions, averaged 102.76 Ibs. per loaded barge, equivalent 

 to 1.08 Ibs. per cu.yd. lifted. 



"By the terms of the contract 1.53 lb. of fuel per cu.yd. were 

 allowed, so that in all respects the results were highly satisfactory." 



The Commission reported in an equally favorable manner on 

 the electric installation. 



The following description of the Pas-de-Calais dredges, translated 

 from the Genie Civile, serves to illustrate a ladder dredge of the 

 hopper type. 



The hopper ladder dredge "Pas-de-Calais," see Fig. 17, was built 

 by the Henry Satre Fils Aine et Cie. for the French Government for 

 the use of several harbors along the English Channel, but mainly 

 for the Naval Station of Boulogne. In order that the dredging 



