But those purposes are not fulfilled by it. A certain large figure is stated as representing the average quantity daily driven through the mains of the City; this quantity is divided by the number of residents within your area, and the inference is drawn that each individual inmate of the City has at his disposal 25 gallons a day; or (after deduction for public purposes and the like) 21¼ for his domestic supply. As an arithmetical conclusion from the premises this may be true: nothing can be less accurate as a practical representation of the facts. An average amount of three million gallons _per diem_ may, or may not, be pumped through the mains of the City: but to calculate the _available water-supply_ from this dividend, without previous deduction for the immense escape of _un-available water_ by waste-pipes or otherwise, gives a most fictitious result. The large waste which naturally arises in the system of intermittent supply has been well illustrated by some evidence given by Mr. Lovick before the late Metropolitan Commission of Sewers, in respect of a particular block of nearly 1200 houses.[47] Some of the houses were of the higher, and many of the poorer class, but the average might be stated to be of the middle class, and to present a fair example of an urban population. The drainage of all these houses was discharged through one main sewer. The run of water through this sewer was carefully watched and gauged every hour, during the night as well as the day, on days when the water was on, that is to say, when the intermittent supplies were delivered, and also on the ordinary days, when the consumption of the houses was from butts and cisterns, into which the intermittent supplies were delivered. The gaugings of the discharge of waste water into the sewer were checked by gaugings of the consumption of water from the butts and cisterns, during the interval of the delivery of the supply by the company. It was ascertained that the average quantity discharged _per diem_ through the sewers was 44½ gallons per house; but it appeared that, on the days when the intermittent supplies of water were on, the quantity discharged _per diem_ was 209 gallons _per_ house. The waste in this district from defects in house apparatus of distribution, incident to an intermittent supply of water, was, on the water days, three and three quarter times greater than the consumption on those days. [47] General Board of Health Report on Supply of Water to the Metropolis, page 120.