time about ten miles of the upper end was advertised, but in consequence of the proposals being considered too high, only about half of it was contracted for. About the middle of May, the contractors generally entered on the work contracted for. In September following, about 16 miles more was put under contract in May, 1838, the balance of the ;

line to Harlem river was put under contract; and the work on the island, except the

grading of the 5th Avenue for pipes, in October following. In consequence of legislative interposition, the Harlem river work was re-let in August, 1839. The 'work was so far completed, as to permit the'water to be let in from the Croton dam on the 22d day of June, 1842 and it was admitted into the distributing reservoir on ;

the 4th of July following. There is yet considerable work to be done at the Croton dam. the receiving and distributing reservoirs, which will probably all be completed in September or early in October. The Harlem river bridge will require at least two years to complete it. At the latter place, a temporary pipe conveys the water across the valley. The following extract is taken from my report of the 12th inst. to the Board of Water Commissioners :

" Since the water was introduced into the '

aqueduct, -the velocity has several times been ascertained, though not in so perfect a manner as I intend to have it done, as soon as other duties will allow the time necessary. Sufficient data, however, have been ob- * As an illustration of the extreme sensibility of water to the smallest declivity, it may be stated that on a long reach of the Erie canal from Lockport, for a distance of sixty miles, the fall is only of half an inch in a mile, aqueducts had an .average declivity of one foot in six hundred. [Ei