370 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



open to criticism, owing to the diversity of practice in esti- 

 mating and recording the quantities removed, and the details of 

 expenditure included in the rate. 



Carlingford Bar. 1 The exceptionally heavy work of cutting 

 through the Carlingford Bar in material consisting mainly of 

 plastic blue clay, occasionally free from all stones, but generally 

 with stones and boulders varying in size from shingle to stones 

 of 4 tons weight, which were slung by divers and lifted by 

 a crane carried by the dredger, cost on an average Is. 5d. 

 per ton = 2s. IJcZ. per cubic yard, including all working 

 charges. The total cost, including insurance, parliamentary ex- 

 penses, and management, was Is. 9d per ton. 



Bilbao. 2 Dredging in sand and mud with a stationary centre- 

 ladder dredger, working to 26 feet deep, and delivering into 

 barges alongside, cost 210 pence per cubic yard, exclusive of all 

 charges for plant. 



Danube. 3 Dredging in hard sticky clay by a single-bucket 

 ladder dredger, and pumping ashore by a mud-pump attached 

 to the same vessel, cost from 2 '04 to 3*88 pence per cubic yard, 

 measured by cross-sections ; this cost included everything except 

 interest and depreciation. 



On the lower Danube, the average cost of dredging in fine 

 sand and clay, and removing by hopper-barges a distance of 

 about one mile, was 4*152 pence per cubic yard, including all 

 charges except interest and depreciation. 4 



California. 5 At Oaklands Harbour, near San Francisco, the 

 average cost, taking over a period of eight years, of dredging 

 in soft dock mud with grab or clam-shell machines, from a depth 

 of 24 feet, removing by barges to a distance of one mile, and 

 discharging, was 3*82 pence per cubic yard, exclusive of insur- 

 ance, taxes, depreciation, and interest. 



Dredging in Oaklands Harbour by means of a suction-pump, 

 with horizontal cutting-gear, attached to the same vessel for 

 reducing the material to be removed to the consistency of mud, 

 raising to the surface and discharging through a line of pipes 

 supported on floating pontoons, to the shore, a distance varying 

 from 1100 to 2850 feet, cost, including all charges, Gd. per 

 cubic yard. 6 



1 M.P.I.C.E., vol. xliv. p. 135. 2 ]lid, vol. li. pp. 245, 255. 



' Ibid., vol. Ixxxix. p. 90. * Ibid., vol. Ixv. p. 270. 



8 Ibid., vol. Ixxxix. p. 94. Engineering, vol. xxxviii. p 30. 



