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 han1 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 45feet 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 carried up plumb, with offsets, the lower section six feet thick, the middle section five feet, and the upper section four feet thick.