| 366 miles of sewers of the first class, or 1,932,480 feet, at 15s. per foot | £1,449,360 |
| 366 miles, or 1,932,480 feet of the second class, at 11s. per foot | 1,062,864 |
| Same length of third class, at 9s. per foot | 869,616 |
| Total cost of the sewers of the metropolis | £3,381,840 |
As this is a lower charge than was paid for the construction of more than three-fourths of the sewers, we may fairly assume that their cost amounted to from three millions and a half to four millions of pounds sterling.
The majority of the house-drains running into the sewers are brick, and seldom less than 9 inches square; sometimes, in the old brick drains, they are some inches larger, and in the very old drains, and in some 100 years old, wooden planks were often used instead of a brick or stone construction, for the sake of reducing cost, and replaced when rotted. The wood, in many cases, soon decayed, and since 1847 no wooden sewers have been allowed to be formed, nor any old ones to be repaired with new wood; the work must be of stone or brick, if not pipeage. About two-thirds of the drains running from the houses to the sewers are brick; the remaining third tubular, or earthenware pipes. The cost, if now to be formed, would be somewhat as follows:—
| 1893⅓ miles of brick drains, 5s. per foot, as average of sizes | £2,499,200 |
| 945⅔ feet of tubular drains, average of sizes 2s. 6d. | 624,800 |
| Total cost of the house-drains of London | £3,124,000 |
The cost of the street or gully drains have still to be estimated.
The present cost of the 9-inch gully-pipe drains is about 3s. 6d. a foot; of the 6-inch, 2s. 6d. Of the proportionate lengths of these two classes of street-drains I have not been able to gain any account, for, I believe, it has never been ascertained in any way approaching to a total return. Taking 1200 miles, however, as quite within the full length of the gully-drains, and calculating at the low average of 3s. the foot for the whole, the total cost of the street-drains of the metropolis would be 950,400l., or, I am assured, one might say a million sterling, and this, even if all were done at the present low prices; the original cost would, of course, have been much greater.
Hence, according to the above calculations, we have the following
Gross Estimate of the Cost of the Sewers and Drains of the Metropolis.
| £ | ||
| 1100 | miles of main covered sewers | 3,500,000 |
| 2840 | miles of house-drains | 3,000,000 |
| 1200 | miles of gully or street drains | 1,000,000 |
| 5140 | miles of sewers and drainage = | 7,500,000 |