COST OF DOCKS. 363 



requiring a special class of plant, for which, on account of its 

 special character, there may be little or no prospect of sale on 

 completion, should bear the whole cost of the plant, in addition 

 to interest on the total amount invested. The actual charge per 

 unit of work depending upon the total quantity of work done, 

 and the number of years over which it is spread. Dealt with in 

 this way, the cost of the Dublin block- work set in place, including 

 forming the foundation, would be as follows : 

 Cost of special plant required for the manufacture and handling of the blocks : 







Diving-bell and barge l 5,454 



Lifting-shears 18,783 



Block-wharf 4,610 



Proportion of other plant, moorings, barges, chain-testing machine, etc. 2 ... 3,400 



32,247 

 Representing a yearly capacity of 6400 cubic yards. 3 



*. d. 



Cost of blocks on wharf, including all materials and labour, suspension- 

 bars, maintenance, etc., of block-wharf, etc. 16 -7- 16 = per cubic yard 100 



Forming foundation 3 -i- 16 = per cubic yard 039 



Lifting, transporting, and setting blocks, including maintenance of plant 



3 -- 16 = per cubic yard 039 

 Shifting moorings, etc. 1 -* 16 = per cubic yard 013 



Total per cubic yard 189 



Assuming such work to have extended over periods of 5, 10, 

 or 15 years, the proportionate charge for plant (with an addition 

 of 5 per cent, per annum) per cubic yard, would be as follows : 



5 years. 10 years. 15 years. 



Charge for plant, and interest per cubic yard 25*00 15'11 11'75 

 Cost of blocks, including labour, materials, and 



maintenance 28-75 28'75 28-75 



53-75 43-86 40'50 



Quay Wall, Brest. The total cost of the special plant 



required, including the barge, with all accessories for lifting, 



transporting, and setting the blocks, block -yard, slipway, and 



hauling-gear did not exceed the sum of 4,000. 4 



The average daily work was 70 cubic yards of block- work 



laid, which, taking 300 5 working days per annum, represents 



about 21,000 cubic yards per year. 



M.P.I.C.E., vol. xxxvii. p. 344. 



It is assumed that this plant was also used for the superstructure. 

 400 X 16 (number of cubic yards per foot run of wall) = 6400 cubic yards. 

 Engineering. 



300 working days per year appears much too liberal an estimate, probably 

 200 days would be much nearer the fact. 



