preferred for the supply of his aqueduct, still adhered to the cold, pure, and abundant springs from the mountains of Tivoli, so Mr. Douglass, disregarding diffi- culties, real and imaginary, and heeding not at all the efforts still to cause the Bronx to be preferred, stood fast for the Croton. The instructions of the Commissioners to the Engineers were, to make " examina- tions of the Croton, Sawmill, and Bronx rivers, in the counties of Westchester and Put- nam, together with their several tributaries ; and to furnish the Commissioners with a map and profile of the country, and their opinion of the quality of the water, the supply that might be depended on in all seasons, and the practicability of conveying it to the city at an elevation of sufficient height to preclude the use of machinery, and answer all the purposes contemplated. The Engineers were also instructed to designate the best and most feasible route for conducting the water, the most fit and proper manner for constructing the conduits and reservoirs, the probable amount of damage that would be sustained by the proprietors of the water to be taken, and of the land it might be necessary to occupy in constructing the required conduits and reservoirs, together with the total amount of cost to the city for completing and putting into operation, the whole project. Mr. Douglass began his surveys late in June, and they occupied him and his party until late in September, and the result was as above stated, a firm conclusion that the Croton should be the source of supply. Two routes, out of marfy examined, were decided on and estimated for, " The Inland," and " The Hudson River " route. The first of these lines followed the valley of the Sawmill river ; its length from the confluent reservoir at Wood's bridge, over the Croton, to the distributing reservoir on CROTON AdUEDUCT. 117 38th street, was a little more than 43 miles — the height above tide, at which the water would stand in the latter reservoir was 117 feet, with a minimum daily supply of about 16,000,000 gallons of running water, and 11,000,000 gallons obtainable from stored water — and at a cost of four and a half millions of dollars for the whole. The Hudson river route was traced wholly along the undulating side of the Croton and Hudson valleys, passing through Sing Sing, Sleepy Hollow and Tarrytown, and so on till it touched the line of the inland route in the valley of the Sawmill river. The length of the route is nearly 47 miles, at an expense of $4,768,197. The plan of construction recommended, was a continuous tunnel or aqueduct in ma- sonry— as preferable both in economy and durability to iron pipes — an open canal being entirely repudiated. The reasons for the preference are thus stated : " On an aqueduct the water flows with an easy natural motion, acting upon its channel with nothing more than its own proper weight, and a friction scarcely apprecia- ble ; and if by an accident its motion should be obstructed, the water having room to expand, would back up and check the velocity of the approaching current without any sensible revulsion upon the sides of the aqueduct : but in a close pipe, having such a de- pression as would be necessary in the present instance, say 130 feet below the head, the action upon the sides of the pipe, would be about 601bs. to the inch. The water being also confined laterally, any impediment would necessarily react in some degree upon its whole volume, as far back as the nearest vent, and it should be observed that a mile of pipe contains more than 700 tons of water. It is true that the probability of any serious impediment is very remote, but even the friction upon so inelastic a substance as water, and under this high pressure and impetus, is a force which at no distant period must im- pair the stability of the work." The principle of the work was, that the water of the Croton should be taken at such height above tide, as to afford a sufficient head to force it across the Harlem river, and to deliver it at the distributing reservoir in the city, at an elevation equal to the supply of the loftiest edifices. The engineer contents himself with having established the practicability of deliver- ing the Croton into the city at a comparatively reasonable cost, and leaves it to be deter- mined by future and more minute examination, what route shall be adopted. Of the quality of the Croton water, Mr. Douglas gives this account : " The supplies of the Croton are derived almost exclusively from the elevated regions of