1901.] HAUPT — METHODS OF IMPROVING OCEAN BARS. 81 



The value of this kind of evidence may be appreciated when it 

 is remembered that the rock composing the inner end of the jetties 

 is submerged and subject to the action of the breakers, so that no 

 sand can lodge upon it as it is driven over. The history of the 

 Charleston operations, covering more than twenty years, is too ex- 

 tensive to be further considered in this connection, but it has suf- 

 ficed to cause the abandonment elsewhere of the submerged jetty 

 theories of 1879. 



5. Dredging. 



Having reviewed the several methods of securing depths by aux- 

 iliary structures and by dynamite, the author concludes that : 



" All things considered, in the present state of the science of bar 

 improvement, dredging appears to be by all means the most eco- 

 nomical and satisfactory method for such work at this place," be- 

 cause, as he adds, u the partial improvement of Brunswick bar by 

 dredging, while it has been very expensive as to the rate per cubic 

 yard, has been quite successful as to the permanence of the improve- 

 ment." 



The permanence of the channel is here attributed to dredging, 

 and the effects of the dynamite are apparently ignored. 



Had a straight channel been dredged through the bar at any 

 time, it would soon have been obliterated : but instead thereof the 

 integrity of the bar was disturbed by heavy charges of dynamite, 

 while the dredge was used as an auxiliary to hasten the formation 

 of the channel, which selected its own locus on curved lines. An 

 inspection of the maps shows that the thalweg of the channel follows 

 a reverse curve, having a trace similar to that of the plan of the 

 reaction breakwater as designed for Aransas Pass. It indicates, 

 therefore, the general form of the curve of greatest ebb energy in 

 open water, and as such confirms the correctness of the theory of 

 the reaction breakwater. The fact that currents move on curved 

 lines is generally ignored in dredging operations with prejudicial 

 results. 



In considering the methods to be pursued at Galveston, the 

 Board of 1886 reported : " The methods are (1) by dredging alone ; 

 (2) by using tidal scour between jetties, aided, if necessary, by dredg- 

 ing. As to the first method, it has already been tried unsuccess- 

 fully There is not sufficient prospect of results commensurate 



with the cost of dredging being obtained and maintained to justify 



