Other Reports and other evidence show that what is described as “earthy matter and sand” is the mac, mud, and the mortar or concrete used in pavement, washed from the surface of the streets into the sewers by heavy rains; otherwise for the most part the proper load of the scavager’s cart.
Further analyses might be adduced, but with merely such variation in the result as is inevitable from the state of the weather when the sewage is drawn forth for examination; whether the day on which this is done happens to be dry or wet[66].
It has been ascertained, but the exact proportion is not, and perhaps cannot be, given, that the extent of covered to uncovered surface in the district drained by the King’s Scholars’ Pond Sewer was as 3 to 1, while that of the Ranelagh Sewer, not far distant, was as 1 to 3, at the time of the inquiry (1848).
“It could not be expected, therefore,” says the Report, “that the Ranelagh Sewer (which, moreover, is open to the admission of the tide at its mouth), in the quantity or quality of the manure produced, could bear any proportion to the King’s Scholars’ Pond Sewer.”
Mr. Smith, of Deanston, stated in evidence, that the average quantity of rain falling into King’s Scholars’ Pond Sewer was 139,934,586 cubic feet in a year, and he assumes 6,000,000 tons as the amount of average minimum quantity of drainage (yearly), yielding 4 cwt. of solid matter in each 100 tons = 1 in 500.
Dr. Granville said, on the same inquiry, that he should be sorry to receive on his land 500 tons of diluted sewer water (such as that from the uncovered Ranelagh Sewer) for 1 ton of really fertilizing sewage, such as that to be derived from the King’s Scholars’ Pond Sewer.
I could easily multiply these analyses, and give further parliamentary or official statements, but, as the results are the same, I will merely give some extracts from the evidence of Dr. Arthur Hassall, as to the microscopic constituents of sewage-water:—
“I have examined,” he said, “the sewer-water of several of the principal sewers of London. I found in it, amongst many other things, much decomposing vegetable matter, portions of the husks and the hairs of the down of wheat, the cells of the potato, cabbage, and other vegetables, while I detected but few forms of animal life, those encountered for the most part being a kind of worm or anælid, and a certain species of animalcule of the genus monas.”
“How do you account,” the Doctor was asked, “for the comparative absence of animal life in the water of most sewers?” “It is, doubtless, to be attributed,” he replied, “in a great measure, to the large quantity of sulphuretted hydrogen contained in sewer-water, and which is continually being evolved by the decomposing substances included in it.”