This objection was offered by Frederick Graff, Esq., the superintendent of the Philadelphia Water Works, who stated that although the dam on the Schuylkill River is raised 6 feet 6 inches above the highest tides, the delay in pumping, occasioned by the tides, averages seven hours out of the twentyfour ; and in full moon tides, from eight to nine hours. The projector of this plan set forth many advantages which he thought would arise from the construction of the dam, but the obstruction to the navigation of the river, the destruction of the shad fishery, and various objections besides those already mentioned, induced the Water Commissioners to reject the idea of building a dam across the Hudson. We have now gone over most of the preliminary steps which were taken before deciding upon the source for a supply of water. --Having fixed upon the Croton River as a stream possessing the requisite advantages for a supply, questions naturally arose as to the manner in which it should be conveyed to the city. The distance being about forty miles, over a country extremely broken and uneven, and following a direction, for a portion of this distance, parallel with the Hudson River, encountering the streams which

empty into it and form deep valleys in their courses. It will

be interesting to notice the different plans which were suggested for forming a channel-way to conduct the water. The following modes were presented : --a plain channel formed of earth, like the ordinary construction of a canal feeder --an open channel, protected against the action of the :