Now, according to reports submitted to Parliament when an improved system of water-supply was under consideration, the daily supply of water to the metropolis is as follows:—
| Gallons. | |
| From the Water Companies | 44,383,329 |
| „ „ Artesian Wells | 8,000,000 |
| „ „ land spring pumps | 3,000,000 |
| 55,383,329 |
The yearly rain-fall throughout the area of the metropolis is 172,053,477 tons, or 33,589,972,120 gallons, 2 feet deep of rain falling on every square inch of London in the course of the year. The yearly total of the water pumped or falling into the metropolis is as follows:—
| Gallons. | |
| Yearly mechanical supply | 19,215,000,000 |
| „ natural ditto | 38,539,972,122 |
| 57,754,972,122 |
The reader will find the details of this subject at p. [203] of the present volume. I recapitulate the results here to save the trouble of reference, and briefly to present the question under one head.
Of course the rain which ultimately forms a portion of the gross wet refuse of London, can be only such as falls on that part of the metropolitan area which is occupied by buildings or streets. What falls upon fields, gardens, and all open ground, is absorbed by the soil. But a large proportion of the rain falling upon the streets, is either absorbed by the dry dust, or retained in the form of mud; hence that only which falls on the house-tops and yards can be said to contribute largely to the gross quantity of wet refuse poured into the sewers. The streets of London appear to occupy one-tenth of the entire metropolitan area, and the houses (estimating 300,000 as occupying upon an average 100 square yards each[62]) another tithe of the surface. The remaining 92 square miles out of the 115 now included in the Registrar-General’s limits (which extend, it should be remembered, to Wandsworth, Lewisham, Bow, and Hampstead), may be said to be made up of suburban gardens, fields, parks, &c., where the rain-water would soak into the earth. We have, then, only two-tenths of the gross rain-fall, or 7,700,000,000 gallons, that could possibly appear in the sewers, and calculating one-third of this to be absorbed by the mud and dust of the streets, we come to the conclusion that the total quantity of rain-water entering the sewers is, in round numbers, 5,000,000,000 gallons per annum.
Reckoning, therefore, 5,000,000,000 gallons to be derived from the annual rain-fall, it appears that the yearly supply of water, from all sources, to be accounted for among the wet house-refuse is, in round numbers, 24,000,000,000 gallons.
The refuse water from the factories need not be calculated separately, as its supply is included in the water mechanically supplied, and the loss from evaporation in boiling, &c., would be perfectly insignificant if deducted from the vast annual supply, but 350,000,000 gallons have been allowed for this and other losses.
There is still another source of the supply of wet house-refuse unconnected either with the rain-fall or the mechanical supply of water—I mean such proportion of the blood or other refuse from the butchers’ and knackers’ premises as is washed into the sewers.
Official returns show that the yearly quantity of animals sold in Smithfield is—