124 The Paris Seicage Irrigation at Gennevilliers. 
receive the quantity of sewage which, sooner or later, must be 
diverted from the river ; and one of the legitimate causes of 
complaint alleged by the adverse petitioners, was the excess of 
flooding with sewage to which the Paris Commissioners were 
tempted, in their anxiety to get rid of their commodity. Flushed 
by their manifest success, they thought that the capacity of the 
land to absorb the sewage had no limits; and we find that in the 
year 1874 some of the fields were favoured with no less than 40,000 
tons of the liquor per acre. No wonder that the level of the 
water-bearing stratum was so raised as to flood some low-lying^ 
cellars, and the bottoms of old gravel-pits. This was not ir- 
rigating the land, but flooding it with a vengeance. 
The Paris engineers had calculated that each acre could easily 
and profitably absorb some 82,000 gallons of sewage, calculating 
upon three crops a year, and a flood of 27,000 gallons for each 
crop. This is evidently excessive, for it would amount to the 
drainage of 360 inhabitants per acre ; whereas in England the 
drainage of 200 inhabitants is, I believe, found by practice to be the 
maximum that can be absorbed by an acre of land under active 
cultivation. On the sewage-farm at Croydon, the sewage from 
165 inhabitants only is used for one acre. It must be admitted, 
however, that the same rule does not obtain for all soils and 
climates. It is obvious that the hot and dry plain of Genne- 
villiers, especially during the summer season, can absorb a much 
larger quantity of sewage than any part of moist England. At all 
events, it plainly appears that the policy aimed at by the Paris 
Sewage Commissioners was not so much to promote the proper 
growth of vegetable market-commodities, as to get rid of the largest 
possible quantity of their sewage ; and however little sympathy 
may be felt for the petitioners, it must be admitted that through 
the lavish supply of sewage, they had some reason to complain. 
The plain of Gennevilliers lies at the base of the high ground 
of the Mont Valerien and Buzenval districts, and receives all the 
rain that falls on that extensive watershed ; and although its 
alluvial gravel measures, in places, from 25 to 45 feet in depth, 
yet when, in addition to natural drainage arising from the 
rainfall, it receives a dose of 40,000 tons of liquid in the course 
of a year, its absorbing capacity is evidently overtaxed, and the 
evils complained of are the result. 
Even in winter, when, the crops being all removed, the land 
remains idle, the sewage is nevertheless poured over the naked 
surface, leaving a black deposit intended to warp the soil and 
increase the depth of its crop-bearing stratum for the ensuing 
season. This is evidently wrong in practice. It has been 
demonstrated in lingland that, together with the soil, vegeta- 
tion is a most energetic deodorising and purifying agent, by 
