An abundant supply of good water is a necessity for every house, and capacious cisterns are a necessity. Two essential requisites are good hydraulic lime and clean pure sand. The hydraulic cement becomes in a few months as hard as sandstone, but the sand must never exceed two parts to one of lime. The cheapest form of cistern is simply a hole dug in the ground with sides sloping like those of a narrow bottomed tub. The water lime mortar is applied directly to these sides, the shape of the sides sustaining the mortar until it hardens. The breadth of such a cistern, if large, makes it difficult to cover, but this may be done with a plank supported by strong scantling, over which should he placed earth to the depth of the lowest frost. There must be a hole through the covering, left for cleaning, which should be curbed, and may admit the pump if the locality is right, or a pipe may go from cistern into cellar below the frost line, and thence to the kitchen. The mortar on the walls should never be less than an inch thick, and they should have at least two coats, and three are better. As the mortar begins to dry in a very short time after mixing, it is best to mix the lime and sand dry, and apply water to small quantities at a time as needed. A more capacious cistern may be made at a greater expense by digging a hole with perpendicular walls, and laying walls of brick in the form of the upper half of a barrel, on which to lay the mortar. This form has a smaller top, and is much more easily covered than the other. The wall should be laid as well as plastered with water-lime. A filtering attachment is made by building a small receiving cistern beside the larger one, with filtering apparatus between them, or a strong wall may be built through the middle of the cistern, receiving the water in one division and filtering it through into the other.