342 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



No. 



No. 



of 



Tests. 



Proportion of Fand in total 



quantity of \\.itcr 

 pumped into hopper. 



Min. Max. Average 



Percent. 

 11-6 



19-0 

 30-0 



Percent. 

 44.7 



50-0 

 64-0 



Per cent. 

 30-9 



47-0 



Propor- 

 tion of 

 Band in 

 overflow 

 water. 



I'er cent. 

 8-0 



2-7 

 8-0 



Propor- 

 tion 

 deposited 



in 

 hopper. 



Per cent. 

 22-9 



36-0 

 3<J-0 



Depth 



of 

 water. 



Feet. 

 27 



KcniarkH. 



Fine sand. 



jSand of a more favour- 



| able and readily 



depositing character. 



Time actually employed in Dredging. It is too often the 

 practice to estimate the capabilities of dredging apparatus from 

 the results of some trial made under the most favourable condi- 

 tions and of a comparatively short duration, and upon this the 

 power of the machine to lift so many cubic yards or tons during 

 a working day is determined. Estimates as to the probable cost 

 and duration of dredging operations based upon such informa- 

 tion cannot fail to be fallacious. It will be found in practice 

 that the time actually employed in effective dredging varies from 

 one-half to not more than two-thirds the total working time. 



The following details of the distribution of time from actual 

 practice will show this : 



Swansea. In forming the deep-sea entrance to the Prince of 

 Wales's Dock : l 



Per cent. 



Repairs to machinery and consequent stoppage 1C'36 



Coaling 1 :;() 



Stoppages by traffic O'lO 



Shifting sinks and chains ... 3*97 



Shifting mooriug-chains 



From extraordinary height of tides 1'35 



Bad weather.. IG'50 



Other-delays s ] :J 



Time actually dredging ID 78 



10000 



Ayr Harbour. Particulars of time in dredging in hard clay, 

 silt, and sand, and removing to sea by a hopper-dredger. 



PIT i .-nt. 



Time occupied in dredging and conveying to sea, letting go moorings, etc. 73 47 



Shifting bushes, repairing machinery, cleaning boilers, etc 4'02 



Coaling ... 



Detentions through bad weather and inspections 



Shifting mooring-chains 



Grounding, etc. ... 



On slip for repairs 3'83 



10000 

 1 M.P.I.C.R, vol. ciii. p. 358. 



