persons from bathing in their aqueduct." Mr. Rhodes, however, has altogether misconceived the construction of the aqueduct proposed by our report, for in- stead of its admitting any of these substances or impurities, it was to be impervious on three sides to any external fluid or substance whatever, and on the fourth, the proposition was, to have it covered with a board or shingle roof. These several inconsistencies have tended to destroy the confidence of the Commis- sioners in the projects of Mr. Rhodes ; and they would not have spent so much time on their examination, had it not been their opinion that the Common Council would expect some notice of a proposition that offered to effect the important object of supplying this city with pure and wholesome water, at a cost two-thirds less than that estimated by our engineer, in his report of 1833. They have, therefore, deemed it their duty to ascertain by actual survey, whether a dam may not be raised at some point nearer the mouth of the river, than that proposed by their report of 1833, from which might be drawn an equal quantity of water, and at the same time save much in the expenditure. To effect the aforesaid object, the Commissioners engaged John Martineau, Esq., civil engineer, to make the necessary surveys, levels, and estimates, having special refe- rence to the erection of a lofty dam at some station on the river nearer its mouth than the place selected by Major Douglas ; to ascertain the damag-e that would ensue by overflow- ing the land and injuring the mill seats ; and to estimate the expense of erecting such dam and compensating those injuries ; to ascertain and report the best plan for conveying the water from said dam to the city ; the quantity per diem that will be conveyed by the plan recommended ; the cost of the necessary excavations, embankments, bridges, cul- verts, and reservoirs, required to deliver the water on a declivity of fifteen inches to the mile, to a receiving reservoir on the high grounds near Harlem river, and from thence across said river to another reservoir of sufficient elevation, near Manhattan ville, (should he be of opinion that these reservoirs will be necessary,) then to a distributing reservoir three or four miles from the City Hall, near Thirty-eighth-street and the Fifth Avenue, preserving an elevation of 117 to 120 feet above tide at said reservoir; but if any of the reservoirs named can be dispensed with, or if additional ones be required, to report the reasons why, and to conform the estimate to the alterations in the plan, should any be commended : to furnish a report in writing, with a profile and map of the survey, show- ing the water line of the basin formed by the dam ; the land that Avill be overflowed on both sides of the river ; the line traced for the aqueduct ; the depth of excavations and the MEMOIR OF THE height of embankments, &c., in order that a plain and comprehensive view of the whole subject may be given. To ascertain whether the cost of erecting a high dam, at or near Garretson's mill, and the consequent damage that will accrue by the overflowing of the land and injuring mill privileges, will be greater than the cost of taking the water from a higher source up the river. The Commissioners have also employed George W. Cartwright, Esq., a civil engi- neer, residing at the village of Sing Sing, and who possesses much local knowledge of the Croton and its vicinity, to run levels on both sides of said river, starting from Garretson's mill, at a height of thirty-eight feet, and carrying his levels up until they loose themselves at the surface of the water, in order to ascertain what quantity of land would be over- flowed with water by the erection of a high dam at the aforesaid station. The next subject which claimed the attention of the Commissioners was the duty imposed upon them by the Ordinance of the Common Council, passed the 24th of July, 1834, which requires them to specify in their report " the probable supply of water that can be obtained within the county." The Commissioners have presumed that this provision of the Ordinance has no allu- sion to the water that may be obtained by deep boring in the rock, or from the sinking of wells, as that subject was thoroughly examined by them in their report of 1833 ; and they have had no reason, since that period, to change the opinion then formed. They have understood, however, an idea has been entertained by some of the members of the Common Council, that a large quantity of water may be