Proceebings of the Folttecjixtc AssociATioy. 983 



In reply we say that it is precisely tlie value of the principle of 

 tidal reserve which we propose to maintain, except that we substitute 

 the extensive surface area of the loM'er Hudson for the limited surface 

 of Flusliing Bay, and do this without the serious losses of tidal 

 supply wliich nov/ occur immediately east of tliis hay, A slight 

 increase of river depth will readily balance all the contents of the 

 bay, and the etiect on the ebb return will be much more direct and 

 powerful. 



A tliird objection will be made on sanitary grounds. It will be 

 urged, tliat the East river tidal currents now carry olf the sewage 

 How of the cities, and to impede these currents will aftect public 

 lioaltli and make solid deposits along the river. 



The answer is, that a very erroneous popular idea exists as to the 

 character of sewage flow, tliat our sewers, so tar from being sluggish 

 vehicles of heavily surcharged matter luive, in reality, so excessive a 

 proportion of water, being the innnediate outlets of the city w^ater 

 and rain supply, that the solid and organic matter is readily held in 

 suspension, and, in fact, is so entirely thus held, that all general 

 attempts to utilize sewage flow for manuring purposes have nearly 

 always tailed on account of this surcharge of water, and that there are 

 wells in public use, in some localities actually less free from solid 

 matter than our sewage. 



While it is true then, tliai the trunk mains wliicli discharge into 

 the river, may at times carry an unusual proportion of sand, street dirt, 

 and other solid matter, and form a deposit at their months ; this 

 material is not objectionable in a sanitary seiise and its amount is com- 

 paratively insignilicant when compared with the present annual 

 deposits 01 river silt, wliich now cost abiiut $300,000 a year to remove, 

 and which this plan will effectually modify. 



Practically, as a question of health, or as a question of dredging, 

 this objection has no special force. The water of the harbor and 

 East river will be twice daily changed and renewed, as now, from 

 the great ocean reservoir ; and if it was not, the whole sewage flow 

 of ]:)otli cities could do no more luirm, at the greatest, than it now 

 does in the precincts where it is created and put in motion, and is 

 constant^ exhaling. 



Taking the daily water supply of both cities at 75,000,000 gallons, 

 the amount of sewage matter will not exceed or equal 11,000 tons, 

 or about 7,000 cubic yards, while the amount of fresh tidal water 

 thrown into the harbor and the rivers above the ]S^arrows, twice a 



