supply of that town from the intermittent to the constant system, and who at the moment had the means of doing so with great accuracy, to institute some experiments with a view to ascertain what, under the constant system, was the actual rate of consumption at each hour of the day. As the result of these experiments, the writer found that, so far from all the people drawing from the mains at the same time, the highest rate of consumption was only about twoand-a-half times the total daily supply; that is to say, that the main and distribution pipes under the constant system should be of a capacity sufficient to supply two-and-a-half times the ordinary daily consumption. Now, as under the intermittent system it was the practice to make the mains and distribution pipes of sufficient capacity to supply four times the ordinary daily consumption, these experiments proved that, so far from larger mains being required under the constant system, they might actually be made of smaller capacity than those required for the intermittent system. It was also shown that, with proper fittings in the houses, the consumption of water under the constant supply system was actually less than that under the intermittent system.

These facts being reported by the Board of Health, and afterwards given in evidence by the writer before a Committee presided over by the late Sir James Graham, and confirmed also by similar results in other cases, brought the controversy to a close in favour of the constant supply system, which is now almost universally adopted, and under which 263,904 out of the 671,888 houses in the London district are now supplied, as stated in the able and interesting report for May, 1884, of Colonel Sir Francis Bolton, Official Water Examiner under the Metropolis Water Act, 1871.

The introduction of the system of constant supply brought about other advantageous changes in the method of distribution. Under the intermittent system the water lay stagnant in the distribution pipes for at least twentytwo out of the twenty-four hours each day, and before

the introduction of filter beds these pipes were practically small settling reservoirs in which the sediment accumulated, and which sediment, when the water was turned on, was driven with the first rush, in a semiputrescent state, into the household storage receptacles.

Under the intermittent system, but little attention was paid to fittings in the houses, as neither those supplying the water nor those receiving it troubled themselves much about waste, which in each case did not last more than an hour or an hour and a half each day. Hence taps, ball-cocks, house supply pipes and other internal fittings were oldfashioned and defective almost beyond description.

With the advent of the constant system, new descriptions of fittings were introduced to prevent waste, and to meet the requirements of the greater pressures at which the water then began to be delivered.

It may be safely affirmed that the constant system has brought about an extraordinary change for the better in all domestic water fittings; those now in general use displaying an amount of skill, ingenuity, and good workmanship far superior to anything ever before known.

Under the intermittent system the distribution pipe necessarily had a "dead end" in each street, because, the water requiring to be daily turned on or shut off, the pipe could only be connected at one end with the feeding main, leaving the other end isolated or "dead." The water near these dead ends became very foul from stagnation, and consequently the dead end required to be frequently washed out. This was effected by drawing a wooden plug fixed in a branch at the end of the distributing main. When this plug was drawn, it was not at all uncommon to see the water spouting out from it tinted with all the colours of the rainbow, from dark purple to the lighter tints, and emitting a most offensive odour, for when the water was shut off, it frequently happened that the distributing pipe was drained by a discharge at some low-lying part of it, and it then became filled with an atmosphere drawn through ground full of gas reek.

Under the constant system these evils, including those resulting from dead ends, are done away with; the distributing pipes being now constantly under pressure, no gas reek or other impurities can enter them, and being connected at each end of the street with the adjoining mains, there is a constant circulation throughout the whole system, whereby stagnation is prevented, as the water is always on the move towards the point of greatest consumption.

Very great improvements have also been made under the constant system, in the construction of the sluice valves for shutting off the water for repairs at any particular point. Under the intermittent system, the sluice valves were only made to shut against the pressure from one side, whilst they are now universally made to shut against the pressure coming from either side or in any direction. These valves, which are called "double faced," are the invention of Mr. James Nasmyth, so well known in connection with the steam hammer. The writer, then an articled pupil to the late Mr. Wicksteed, engineer to the East London Waterworks, had the privilege of assisting Mr. Nasmyth in preparing the first rough drawing of these "double-faced" sluice valves; and he well remembers the instantaneous rapidity with which that great mechanician not only grasped the point to be attained, but within an hour had so completely solved the difficulty to be overcome, that whilst alterations have been made in minor details, no practical improvement has been effected in that first design of his.

The method of connecting the house services with the main pipes has also undergone a great improvement. In early times the connection was made by driving a brass ferrule into a hole chipped or drilled through the main pipe. These ferrules were apt to be dislodged, and frequently blew out, and the fixing of them obliged the water to be shut off from the whole street during this occasionally tedious operation. These connections are now made by screw threaded ferrules, tapped securely into

the pipe by an instrument which obviates the necessity for any stoppage of the supply to other houses whilst the operation is being performed.

The arrangements also for the supply of water for fire extinction have been very greatly improved since the introduction of the constant supply system. In former times, in the event of a fire, the first thing was to find the turncock to turn the water into the main. This done, the old wooden plug had to be knocked out, often a work of time and difficulty; and then until all the empty tubs and tanks were filled up in the street there was practically very little pressure at the plug, and the supply was consequently scanty for some time. Thus most precious moments were lost. Now, on the contrary, the fireman goes to the nearest hydrant, inserts his standpipe, turns on the water from the constantly charged main pipe, and in a much less time than it previously took to call the turncock, he has a stream of water pouring into or over the burning building at the rate of 200 or 300 gallons a minute, and under a pressure sufficient to knock a strong man down at a distace of fifty yards from the nozzle of the fire-hose, and that without the intervention of any fire-engine.

Another little machine which has proved itself to be of great value in connection with constant supply, is the "Waste Water Detector," invented by Mr. Deacon, the engineer to the Liverpool Corporation Waterworks. This machine indicates and registers the flow of water passing through any particular pipe at any moment of time, and by its agency all undue waste and leakage are easily detected and traced. Thus the modern appliances in connection with distribution, if properly used and directed, are now nearly all that can be desired.

Except in very special cases, the writer is not an advocate for the "Dual System," that is a system under which two classes of water are introduced into a town; the one for dietetic purposes, and the other for washing, street-watering, sewer-flushing, fire-extinguishing purposes, &c. The dual system necessarily involves the laying of a

duplicate set of mains, and the fixing of a duplicate set of house fittings, with all the attendant annoyance and expense.

There may be cases where the circumstances are so peculiar as to make the dual system a necessity, and then the difficulty must be faced; but generally it will be found cheaper and better to manipulate the supply so as to make sure that none but water of a high class shall ever enter the mains, and so as to effect the whole work of distribution by one set of pipes and fittings.

WATER SUPPLY FOR FIRE
EXTINCTION.

By J. H. GREATHEAD, M.Inst.C.E.

WHEN it is considered how vast is the havoc wrought by fire every year, and that we depend upon a supply of water, in all cases, to prevent much greater ravages, the importance of this subject will be at once recognised.

In London alone, it has been calculated on reliable data that the destruction of property in 1882 amounted to at least 24 millions sterling, and last year it was probably more; and it has been stated by a very good authority, Mr. Edward Atkinson, of the Boston Manufacturers' Mutual Insurance Company, that the losses by fire in the United States and Canada in the five years ending January 1st, 1879, amounted to 824 millions sterling, while the cost of insurance companies and fire departments in the same period amounted to 55 millions more, or together to an average of 27 millions sterling per annum.

It is difficult for the mind to grasp such figures; the last, however, is about equal to the whole rateable annual value of the metropolis.

If such losses as these were inevitable, it would be of little profit to refer to them, but it is because I believe