Proceedings of tee Polytechnic Association. 977 



and from Montauk Point to Bridgeport 27.1 miles. If, then, the 

 velocity of this wave was equal in the harbor, the East river, and the 

 sound, the meeting of the full tides would be about one-half hour's 

 flow east of Bridgeport; but in consequence of the curvatures and 

 contractions of the East river, the travel of the harbor wave in the 

 sound is delayed, and while the first of its flood passes a long distance 

 eastward of Throg's Neck, the superior velocity of the sound tide, 

 enables it to arrest this flow, so that with a crest level of 1.6 feet 

 above that of Bridgeport, at Oyster Bay, twenty miles east of Throg's 

 Neck, four-tenth above that of Land's Point and Throg's Neck, the tidess 

 mutually balance their forces in that vicinity. Then occurs the ebb 

 flow in opposite directions from the vicinity of Throg's Neck, as shown 

 by the coast survey charts and the experience of navigation. It 

 results from this action that a considerable portion of the harbor 

 flood, probably fifteen per cent, thrown into the sound through these 

 advantages in distance of travel and time, is lost to the ebb flow of 

 the harbor, since the sound ebb prevents its return at Throg's Neck. 



When the tides turn at Throg's Neck, another important but 

 entirely natural process occurs. The sound ebb proceeds toward 

 Montauk Point with a free flow ; but the harbor ebb, having a 

 restricted Hellgate channel to pass, returns w*ith less velocity than, 

 the flood run, its feeding supply being also diminished. So we see- 

 by the current charts of part of this passage that a flood run of Z>.OT 

 knots per hour near Polhemus' Dock has an ebb of 2.65 ; opposite- 

 Hallet's Point a flood of 7.83 to 11.1 knots for an ebb of 4.4; on the- 

 east side of Blackwell's Island a flood of 4,3 knots has an ebb of 3,53' 

 to 3.96. The action at Buttermilk Channel of a depleted East river 

 ebb, is thus explained : At Sandy Hook, where' the ocean wave regu- 

 lates the outlet in part, the ebb has about nine minutes less duration 

 than the flood. 



These simple •but decisive facts prove that the East river is nothing- 

 less than a continual outlet toward Montauk Point, of an important 

 part of the legitimate flood tide and fresh water supply of New York 

 harbor, pouring in tliAt unnatural and hurtful direction, the volumes- 

 which, properly retained and assisted, would sweep out to sea at 

 Sandy Hook with a largely increased ebb, and with an absolute and 

 permanent effect. 



This improvement in correcting this great defect corrects others : 



The importance of the Hudson rivei' as a tidal reservoir to the 

 Sandy Hook channel is repeatedly urged in the reports of the harbor 



[Inst.] 'B2 



