Proceedings of the P olytecrnic Association. 975 



Advantages and Objections, 



To compass tlie range of advantages presented by tin's plan in a com- 

 pact form, without expanding the several branches of details in argu- 

 ment, however interesting, and perhaps essential some of them may be, 

 the following outline sketch may be made : 



It 19 claimed then, first of all, that if this plan can be demonstra- 

 ted to contain a direct and immediate improvement of the Sandy 

 Hook channel, this feature alone will justify its urgent .pressure 

 toward construction. 



All the scientific surveys and reports on this point make it clear, 

 that the main entrance to our harbor is in a very unsatisfactory con- 

 dition. Not only does it appeal-, as per report of the harbor com- 

 mission of January, 1857, page 33, that it was not then " safe for a 

 vessel drawing twenty-three feet to go to sea, except at half or full 

 tide." But it is also made evident, that there is a gradual northerly 

 movement of the sand formations at the Hook, a gradual restric- 

 tion of the outlet; a continual deposit of silt on the several bars, 

 and an annual change in the direction of the main ship channel. 

 This arises mainly from the annual deposit of harbor silt not duly 

 carried to sea, caused partly by the silt brought down by the freeh 

 water affluent of the harbor, and partly by the special deposits of 

 dredged material carried down the harbor to a convenient point and 

 there dropped, to be again taken up by tidal action and returned 

 where it came from, or redeposited at Sandy Hook and other 

 points. 



The scientific evidence which proves the annual increase of deposit 

 at the Sandy Hook outlet is abundant and conclusive in the coast 

 survey and harbor commission reports, surveys and charts. In 1857 

 they state that Sandy Hook has advanced toward the channel, 

 "within a century, one mile and a quarter, and for the last twelve 

 years at the rate of one-sixteenth of a mile per annum." In twenty 

 years, " in the main ship channel alone, there has been an actual 

 deposit of 2,532,600 cubic feet (93,800 yards)." The main channel, 

 which once carried forty feet water, is now restricted to twenty-tliree, 

 and is being gradually forced into Sandy Hook Bay, and in a width 

 of outlet of about seven and one-fourth miles is the only main 

 channel which remains. 



It is evident, without much appeal to the authorities of the science 

 of hydrology, that this effect at the ship channel arises from a lack of 

 scouring power in the flood and ebb tides, but chiefly the latter, and 



