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 depression 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 impair 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 delivering the Croton into the city at a comparatively reasonable cost, and leaves it to be determined by future and more minute examination, what route shall be adopted. Of the quality of the Croton water, Mr. Douglas gives this account :