82 HAUFT — METHODS OF IMPROVING OCEAN BARS. [May 3, 



further experiment." The second method of twin jetties was there- 

 fore resorted to, but the tidal scour did not deepen the bar as ex- 

 pected, since the jetties were 7000 feet apart. Hence a cut was 

 dredged along the axis of the channel. It was begun April 11, 

 1895, when the depths were about fifteen feet on the crest of the bar. 

 But it did not remain straight, as the resultant drift soon swung the 

 channel to the south on its normal curve, with a radius of five 

 miles, and it now crosses the line of the south jetty produced. 

 Many instances might be cited of the failure to secure channels in 

 the open sea by dredging, especially where there is a prevailing 

 littoral drift, but the fact is so generally recognized that it is not 

 necessary to extend this discussion further than to add a few words 

 as to cost. 



It has been officially certified that the total cost of the work 

 done by the contractor at Brunswick was $253,646.15 for a 

 gain in depth of 5.6 feet, giving $45,293.95 per foot of depth 

 secured. The author, however, states that dredging has been 

 done on the Mersey bar at Liverpool for two and one-third 

 cents per cubic yard, and says that fifteen cents is a fair price 

 for this class of work. He then proceeds to estimate the 

 quantity of material in place which it would have been nec- 

 essary to remove to secure the present channel, and figures that 

 1 25,000 cubic yards at fifteen cents would have cost but $18,750 for 

 the entire work, and that the actual cost of $253,646.15 was there- 

 fore excessive. He concludes : "The cost to the Government of all 

 material removed, whether usefully removed or otherwise, has been 

 $1.13 a yard, more than seven times the cost of ordinary dredging." 



If it were only necessary to remove 125,000 yards to secure the 

 channel, the cost would have been $2.03 per yard. At $1.13 there 

 must have been 224,400 yards taken out, but as a matter of fact the 

 actual cube of excavation was very much larger than this, since the 

 enormous bank " which always moves very positively in one direc- 

 tion" was constantly supplying material to the channel. 



The radical error in this computation of cost arises from regard- 

 ing the volume of the material as a constant over a given area of 

 the bar, and considering only the net loss or gain due to local 

 changes in form of cross section. The absurdity of this method is 

 seen from the table on page 14 of the report, wherein a strip 

 6370 feet long and of variable widths is taken for an estimate. I- 



