PRESENT PROBLEMS OF TECHNOLOGY 581 



sels to clear light, wait for favorable conditions of wind and tide, 

 or store their freight for lack of sufficient draught. It is even now 

 true that the most economical vessel cannot be built because of 

 the existing limitations of channels and ports, not yet removed, 

 and which, notwithstanding the great improvements in hydraulic 

 dredging-plants, cannot be permanently relieved by these mechan- 

 ical devices. 



The great fertile plains and deltas at the mouths of sedimentary 

 rivers are but the natural depositories for the detritus fed to them 

 by their hydraulic conveyors whose source is in the highlands, 

 which streams carry hundreds of millions of yards of earthy matter 

 to the sea, where it must ultimately rest. 



The problem here is, then, so to dispose of this deposit by natural 

 agencies as to prevent its obstructing the channels of commerce. 

 This can be accomplished by utilizing the potential energy of the 

 stream itself by means of a concave resisting medium, placed across 

 the bar in such position as to develop a reaction and scour, which 

 changes the form of the channel and transports the sediment later- 

 ally to the counterscarp thus created, and from which the waves 

 and littoral currents remove it. 



This method has been demonstrated by actual experience and 

 is found to effect great economies in cost of construction and main- 

 tenance, since the trace of the work is less than half as long as that 

 required by the preexisting methods, and there is no correspond- 

 ing bar advance, but an automatic adjustment of the channel and 

 dump to the requirements of that particular stream arid locality. 



This is a physical problem which has impressed itself with more 

 and more emphasis, because of the rapid strides made in commerce 

 and manufactures and the greatly increased demands for larger 

 tonnage and correspondingly deeper channels. The mere cutting 

 of a ditch across an ocean bar in the face of the ever active forces 

 which created it is not a satisfactory nor an economic solution of 

 this question. It is estimated that the automatic reaction break- 

 water would have saved over fifty millions of dollars in the past 

 decade in this country alone, had it not been for the conservatism 

 which was unable to concede its advantages prior to an actual 

 demonstration, and which has debarred its general introduction. 



This incident is cited, without detail of the resistances it has 

 overcome, merely to illustrate the truths of the general principles 

 enumerated, as to the elements opposed to progress, in the intro- 

 duction to this paper. 



Returning now to the general theme as to the future of economic 

 transportation, it will -be found necessary to devote large appro- 

 priations from the treasuries of states and nations to the better- 

 ment of the public highways, for the general welfare and as feeders 



