The conditions of supply in the two cases differ in being from a general and public source in the one and from a special and private source in the other. In each case, the consumer has to control the purity and application of the supply after its delivery into the dwelling; and in the second case he is further responsible for the character and quantity of the supply before delivery. The second case, therefore, in a great measure covers the first, and demands extended treatment. _Amount required._--The first consideration is the quantity of water required. The supply to towns from waterworks is usually expressed in “gallons per head of population per diem,” and varies exceedingly, much of the variation being due to waste. This is especially the case in towns where the supply is intermittent. In several towns having a constant supply, steps have been taken systematically to measure the water supplied to different streets and districts, and it has been found that, without restricting the supply in any way, the consumption of water has been immensely reduced, simply by sending inspectors to make a house-to-house visitation and search out and repair leaky pipes and defective taps and ball-cocks. It is by no means an unusual thing for the consumption to be reduced one-half by inspections of this kind, showing that at least one-half of the water which was previously supplied to the houses was simply wasted through leaky fittings. Many people are inclined to think that waste of this kind is not a bad thing, as it must help to keep the drains flushed. Field points out that this is quite a mistake. A small dribble of water from a leaky pipe or a leaky tap, though it will waste a great deal of water in the course of 24 hours, is perfectly useless for flushing the drains. What is wanted for this is the sudden discharge of a large quantity of water. The dribble of water from leaky pipes and taps does no good in any way, but simply wastes what might be usefully employed, and in many cases causes a supply to run short which would otherwise be ample for all legitimate uses. Another point that it is difficult to realise is the large quantity of water which will run to waste through what is apparently a very small leak. The quantity leaking looks so small in comparison with the quantity running when a tap is open, that one is inclined to think it perfectly insignificant, forgetting that the leakage goes on continuously night and day, whereas the tap is only open for a few minutes. In country houses, where it is often difficult to obtain a sufficient supply of water, it is particularly important to bear in mind the serious influence that leaky pipes and taps have on the consumption, and never to allow such leakage to go on for any length of time.