One object of this arrangement is to obtain the greatest breadth with a given quantity of material ; another is to afford an opportunity to examine the work so as to guard against leakage and another, to prevent any moisture finding its way through to the exterior so as to cause injury to the wall by the action

of frost. This kind of open work of the wall rises to within about 8 feet of top water line. Inside of these walls an

embankment of puddled earth is formed with suitable breadth of base to give security to the work, and the face of this earth next to the water is covered with a wall of hydraulic masonry Ij- foot thick. The top of the embankment is covered with stone flagging, forming a walk around the top of the Reservoir. The bottom of the Reservoir has a covering of concrete 1 foot thick ; thus when it is empty there will be seen two basins having the sides and bottom formed of masonry. A section of the wall of one side of the Reservoir, including the embankment, is 17 feet wide at the top, 35 feet

wide 16 feet below the top, and 76 feet wide at the bottom :

the cornice projects on the outside and the coping on the inside so as to make the width of the top 21 feet. An iron railing bounds the outside and inside of the walk around the top. The outside of the Reservoir is built on a slope of one sixth its height, or two inches to the foot, and an Egyptian cornice projects at the top of the main walls and the pilasters.