London alone among great capitals is supplied with water by private companies. They are, however, under government supervision, and the rates charged for water are regulated by law. There are eight companies, each of which supplies its own separate district, so that there is no competition whatever. One of the companies supplying 460,000 people uses only ground-water drawn from deep wells in the chalk, but the other seven companies depend mainly upon the rivers Thames and Lea for their water. All water so drawn is filtered, and must be satisfactory to the water examiner, who is required to inspect the water supplied by each company at frequent intervals, and the results of the examinations are published each month.

In 1893 the average daily supply was 235,000,000 gallons, of which about 40,000,000 were drawn from the chalk, 125,000,000 from the Thames, and 70,000,000 from the Lea. Formerly some of the water companies drew water from the Thames within the city where it was grossly polluted, and the plagues and cholera which formerly ravaged London were in part due to this fact. These intakes were abandoned many years ago, and all the companies now draw their water from points outside of the city and its immediate suburbs.

The area of the watershed of the Thames above the intakes of the water companies is 3548 square miles, and the population living upon it in 1891 was 1,056,415. The Thames Conservancy Board has control of the main river for its whole length, and of all tributaries within ten miles in a straight line of the main river, but has no jurisdiction over the more remote feeders. The area drained is essentially agricultural, with but little manufacturing, and there are but few large towns. In the area coming under the conservators there are but six towns with populations above 10,000 and an aggregate population of 170,000, and there are but two or three other large towns on the remaining area more than ten miles from the river. These principal towns are as follows:

Guildford is outside of the conservators’ area. All of the above towns treat their sewage by irrigation.

Among the places that are regarded as the most dangerous are Chertsey and Staines, with populations of 9215 and 5060, only 8 and 11 miles above the intakes respectively. These towns are only partially sewered and still depend mainly on cesspools. An attempt is made to treat the little sewage which they produce upon land, but the work has not as yet been systematically carried out. There are also several small towns of 3000 inhabitants or less upon the upper river which do not treat their sewage so far as they have any, but, owing to their great distance, the danger from them is much less than from Chertsey and Staines. Twenty-one of the principal towns upon the watershed have sewage farms, and there are no chemical precipitation plants now in use.

Boats upon the river are not allowed to drain into it, but are compelled to provide receptacles for their sewage, and facilities are provided for removing and disposing of it; and as an additional precaution no boat is allowed to anchor within five miles of the intakes.

The conservators of the river Lea have control of its entire drainage area, which is about 460 square miles, measured from the East London water intakes, and has a population of 189,287. On this watershed there is but a single town with more than 10,000 inhabitants, this being Lutton near the headwaters of the river, with a population of 30,005. The sewage from Lutton and from seventeen smaller places is treated upon land. No crude sewage is known to be ordinarily discharged into the river. At Hereford, eleven miles above the East London intakes, there is a chemical precipitation plant. The conservators do not regard this treatment as satisfactory, and have recently conducted an expensive lawsuit against the local authorities to compel them to further treat their effluent. The suit was lost, the court holding that no actual injury to health had been shown. It is especially interesting to note that of the thirty-nine places on the Thames and the Lea giving their sewage systematic treatment there is but a single place using chemical precipitation, and there it is not considered satisfactory. Formerly quite a number of these towns used other processes than land treatment, but in every case but Hereford land treatment has been substituted.

In regard to the efficiency of the sewage farms, it is believed that in ordinary weather the whole of the sewage percolates through the land, and the inspectors of the Conservancy Boards strongly object to its being allowed to pass over the surface into the streams. The land, however, is for the most part impervious, as compared to Massachusetts and German sewage farms, and in times of heavy storms the land often has all the water it can take without receiving even the ordinary flow of sewage, and much less the increased storm-flow. At such times the sewage either does go over the surface, or perhaps more frequently is discharged directly into the rivers without even a pretence of treatment. The conservators apparently regard this as an unavoidable evil and do not vigorously oppose it. It is the theory that, owing to the increased dilution with the storm-flows, the matter is comparatively harmless, although it would seem that the reduced time required for it to reach the water-works intakes might largely offset the effect of increased dilution.

The water companies have large storage and sedimentation basins with an aggregate capacity equal to nine days’ supply, but the proportion varies widely with the different companies. It is desired that the water held in reserve shall be alone used while the river is in flood, as, owing to its increased pollution, it is regarded as far more dangerous than the water at other times; but as no record is kept of the times when raw sewage is discharged, and no exact information is available in regard to the times when the companies do not take in raw water, it can safely be assumed that a considerable amount of raw sewage does become mixed with the water which is drawn by the companies.

The water drawn from the river is filtered through 113 filters having an area of 116 acres. None of the filters are covered, and with an average January temperature of 39° but little trouble with ice is experienced. A few new filters are provided with appliances for regulating the rate on each filter separately and securing regular and determined rates of filtration, but nearly all of the filters are of the simple type described on page 48, and the rates of filtration are subject to more or less violent fluctuation, the extent of which cannot be determined.

The area of filters is being continually increased to meet increasing consumption; the approximate areas of filters in use having been as follows:

There has been a tendency to reduce somewhat the rate of filtration. In 1868, with 51 acres of filters, the average daily quantity of water filtered was 111,000,000 gallons, or 2,180,000 gallons per acre. In 1884, with 97 acres of filter surface, the daily quantity filtered was 157,000,000 gallons, or 1,620,000 gallons per acre; and in 1893, with 116 acres of filter surface and 195,000,000 gallons daily, the yield per acre was 1,680,000 gallons.

Owing to the area of filter surface out of use while being cleaned, the variations in consumption of water, and the imperfections of the regulating apparatus, the actual rates of filtration are often very much higher and at times may easily be double the figures given.

Evidence regarding the healthfulness of the filtered river-water was collected and examined in a most exhaustive manner in 1893 by a Royal Commission appointed to consider the water-supply of the metropolis in all its aspects with reference to future needs. This commission was unable to obtain any evidence whatever that the water as then supplied was unhealthy or likely to become so, and they report that the rivers can safely be depended upon for many years to come.

The numbers of deaths from all causes and from typhoid fever annually per million of inhabitants for the years 1885-1891 in the populations receiving their waters from different sources in London were as follows:

The population supplied exclusively from the Lea by the East London Company is of a poorer class than that of the rest of London, and this may account for the slightly higher death-rate in this section. Aside from this the rate is remarkably uniform and shows no great difference between the section drinking ground-water only and those drinking filtered river-waters. The death-rate from typhoid fever is also very uniform and, although higher than that of some Continental cities with excellent water-supplies (Berlin, Vienna, Munich, Dresden), is very low—lower than in any American city of which I have records.

In this connection, it was shown by the Registrar-General that there is only a very small amount of typhoid fever on the watersheds of the Thames and Lea, so that the danger of infection of the water as distinct from pollution is less than would otherwise be the case. Thus for the seven years above mentioned the numbers of deaths from typhoid fever per million of population were only 105 and 120 on the watersheds of the Thames and the Lea respectively, as against 176 for the whole of England and Wales.