A parapet wall will be laid on each side of the bed of the pipes, to support the earth covering, which is to be four feet deep above the pipes, to protect the water from the effects of frost.

There will be an influent pipe chamber at the termination of the aqueduct on the north, or Westchester side of the river, in which the pipes are to be inserted. Commencing on this side of the river, at the influent pipe chamber, the pipes descend nearly with the slope of the hill, forming an angle near its base, and thence to the lowest level which ;

determines the top of the foundation wall for the pipes, at four feet above flood tide. This level is continued to the angle, before rising to the channel arch, from whence an inclined plane carries the pipes to the effluent pipe chamber, on the New York side of the river. It is proposed to arrange the structure of the chambers, and foundation for the pipes, to accommodate four 36 inch cast iron conduits, whenever so many shall be required. Four three feet pipes, according to the calculation of the engineers, will deliver 49,843,984 gallons of water every twenty-four hours which is about the quantity calculated to be ;

delivered by the aqueduct, and nearly the average quantity running in the Croton. River. It is proposed, therefore, to insert only two of these pipes at present ; they being deemed more than sufficient to supply the city with water for many years to come. This estimate is reported in detail likewise, and amounts in the aggregate as follows :