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 :

" The supplies of the Croton are derived almost exclusively from the elevated regions of the Highlands' in Westchester and Putnam counties, being furnished by the '

pure springs, which so remarkably characterise the granitic formation of that region. The ponds and lakes delineated on the map, and spoken of in a former part of this re-

MEMOIR OF THE

port, are among the number of these springs ; many of them 3 or 400 acres in extent, and one as large as a thousand acres. All these ponds are surrounded by clear upland shores, without any intermixture of marsh ; and the surrounding country, cultivated as it is generally, in grazing farms, presents an aspect of more than ordinary cleanness. The water, as might be expected under such circumstances, is perfectly soft and clear, much superior in the former respect to the waters of our western lakes, and fully equal in the latter.