The apparatus will now be in the condition to afford a regular supply of softened water; all that will be necessary to insure its continuous action will be that at certain stated intervals dependent upon the rapidity with which the water is used--but which interval should not be less than eight hours--the following things should be done: (1) The float must be raised out of the tank last emptied. (2) The float must be lowered into the tank last filled. (3) The weight, M, must be raised, and the ring of the chain shifted to the next stud on the wheel, K. (4) The clear lime water found in the tank, N, must be turned into the tank last emptied. (5) The requisite quantity of lime must be put into the tank, N. (6) The requisite quantity of water must be drawn off from the tank last filled into the tank, N. (7) The contents of tank, N, must be thoroughly mixed by means of the air pump. The quantity of lime to be used for each tankful of water must depend upon the hardness of the water, ¾ oz. being required for each tankful for each degree of hardness. It is desirable, however, always to have an excess of lime in the tank, N, so as to insure obtaining a saturated solution of lime. When first mixed the contents of the tank, N, will have a creamy appearance, but when the superabundant lime has subsided the supernatant liquid will be a perfectly clear saturated solution of lime. Therefore, in the first instance, 3 lb. of lime should be put into the tank, N, and subsequently each time such a quantity of lime should be added as is found to be necessary by the method hereinafter described. The quantity of the saturated lime water to be run into each of the softening tanks, Q, S, and V, will depend upon the hardness of the water. For every degree of temporary hardness a depth of 1-6/10 in. of the contents of the tank, N, will be required; so that if the water has 14 deg. of temporary hardness, then 22½ in. in depth of lime water must be run off into each of the tanks, Q, S, and V. In the first instance an excess of lime may be used, and the softened water tested by means of nitrate of silver in the following manner: A solution of 1 oz. of nitrate of silver in a pint of twice distilled water should be obtained. Having let two or three drops of this solution fall on the bottom of a white tea cup, slowly add the softened water; then if there be any excess of lime, a yellow color will show itself, and the quantity of lime water used must be reduced until only the faintest trace of color is perceptible.--_The Engineer_. [Illustration: Fig. 6] * * * * * IMPROVED WATER METER.