Southwood Smith [...] had recommended that the improvements made in the wealthier districts, i.e. the provision of houses drains and water-closets discharging directly into the sewers, should be extended to the poorer quarters [48]. Chadwick admitted that these improvements save the delay and the previous accumulation and the expense of the old means of removal [54-55]. But in the first place there were no sewers in the poorer quarters. In the second place the remedy would prove worse than the disease; for the seweres were so constructed as to accummulate deposits which while they remained there gave off noxious gases. It was by one doctor that of all the cases of severe typhus he had seen, four-fifths were either in houses where the drains to the sewers were untrapped, or which, being trapped, were opposite gully-holes [F 220-221].

In Chadwick's view the first and second objections were not nearly so important as the third. It was a great pity, for could the sewers only ve unoroved, the use of the water-closet was by far the most convenient, cleanlym and economical mode of getting rid of the house refuse. This cardinal defect in the construction of sewers was remedied by te discovery of a Mr John Roe, engineer to the Holborn and Finsbury Commission of Sewers. His discovery, adapted by Chadwick, became the fulcral point of an entirely new conception of town sanitation, the method of circulation instead of stagnation, the arterial system of town drainage [F 221].

John Roe---"perhaps the only officer having the experience and qualifications of a civil engineer"[Sanitary Report 55; L 53]. Since his appointment in 1820 he had succeeded in introducing a number of improvements in the face of the conservatism and obtuseness of his employers. Roe had devised a system of flushing which halved the cost of cleansing the sewers; he had reduced the size of drains for short streets and courts from 4ft.6in. x 2ft.15in, in diameter. and, findinf that the practice of joining sewers at angles (frequetly even right angles) caused eddies and the deposit sediment, and obstruct the current of water, he had persuaded the Commissioners to require that curves should formed in the sewers with a radius of not less than twenty feet. Chadwick was delighted, and set Roe to work on a series of experiments to ascertain the most economical size of pipe for drains and sewers and the best materials for their construction. The arterial-venous system if town drainage, which he elaborated in the next two years, owed much to these suggestive experiments by John Roe [L 54].

Roe found out that a new type of sewer, well supplied with water, could sweep away any solid matter within it immediately, cheaply, cleanly, and without the trace of deposit. Connected to such sewers the water-closet or the soil-pan might duscharge their contents through the house drain straight into the sewer, and only a few hours afterwards the refuse would have reached the river. Roe's discovery was the use of steep gradients together with the egg-shaped sewer [ibid.].

[...] the carrying water into every house, the removal of all excreta in suspension in water by means of the soil-pan, etc., the proof that the water-closet may be made mechanically cheaper than cesspool... the evidence as to the application of liquid manures...; with this we complete the circle and realize the Egyptian type of eternity by bringing as it were the serpent's tail into the serpent's mouth [EC to Lord Francis Egerton, 1 October 1845; F 222].