the southern 30 feet depth. But they are not fully excavated in some parts, where rock occurs, it not being deemed sufficiently important to incur the expense of ex- cavation in rock for the increased capacity that would be obtained. The reservoir has a capacity of 150,000,000 imperial gallons, as it now stands. The reservoir is formed with earth banks, the interior having regular puddled walls to render them impervious to water ; the outside protected by a stone wall, laid up on a slope of one horizontal to three vertical, the face laid in cement mortar, and the inside dry ; the inside is protected by a dry slope wall, laid on the face of the embankment, which slopes 1| horizontal to one vertical. The embankments are raised four feet above the top of water line, and are 18 feet wide on the top, excepting the high banks on the sourthern division and the western bank on the northern division, which are 21 feet wide. The greater part of the embankments for the northern division are of moderate height ; but a portion of the eastern and western banks of the southern division are 38 feet high above their base. Vaults or brick arch ways. are constructed, in which iron pipes are laid, so arranged that the pipes from the northern di- vision connect with those from the southern division, and thence pass off to the distributing reservoir, and to supply the adjacent districts. The main vault is on the eastern side ; it is 540 feet long and is 16 feet span ; that on the western side is 400 feet in length, and 8 feet span ; designed for supplying at a future day the district on the north river side above 42d street. The pipes are all provided with stop cocks, and so arranged that they can receive the water from either division ; except one pipe from each division, that leads to the dis- tributing reservoir. It is intended to carry three lines of pipes, each three feet diameter to the distributing reservoir, (at present only two lines are put down,) and the arrangement will allow two pipes to be drawn from either division, so that in the event of emptying one division for repairs, the other would supply two pipes for the distributing reservoir, and all other pipes having a connection with each division would be in full supply, notwith- standing the suspension of one division. A pipe is put through the division bank, with a stop cock, to allow the water or not, as may be desired, to pass from one division to the other. The aqueduct intersects the reservoir at right angles with its westerly line, and 252 feet south of the north-westerly corner. At this point a gate chamber is constructed, with one set of gates to pass the water into the northern division, and another set to pass it into a continued conduit of masonry, constructed within the embankment of the reservoir, to the angle of the southern division, where it enters by a brick sluice into this division. This arrangement gives the power of directing the water into either division, or both, at the same time, as may be desired. In the division bank, a waste weir is constructed to carry off the surplus water from either division, when it rises to the proper height. DISTRIBUTING RESERVOIR. This reservoir occupies the highest ground in the vicinity, and higher 1 han any part of the city south of it ; the site is generally known as Murray Hill. In order to mair tain the elevation of the water, it was necessary to raise the walls of CROTON AdUEDUCT. 21$ ihe reservoir to an avarege height of 45 £ feet above the grade of the streets that bounded it on three sides, the greatest height being 49 feet, and the least 39 feet ; the foundations were sunk five feet below the grade of the streets. The walls are of hydraulic stone masonry, constructed with openings, to reduce the quantity of masonry and give a more enlarged base. The openings are made by an exterior and interior wall, connected at every ten feet by cross walls, which are carried up to within 17 feet of the top, and there connected by a brick arch thrown from one to the other, and the spandrels between them levelled up solid, and a course of concrete put over the whole, 6 inches thick, which reaches a level 10 feet below the top, whence the exterior wail is carried up single to the top. The exterior wall has a bevel of one to six, and is uniformly four feet thick from the bottom to the top of the connecting arches • the inner wall is