Tlie Paris Sewage Irrigation at Gennevilliers. 
117 
The storm of angry remonstrances that arose from the 
dwellers on the banks of the Seine, when the sluices of the Paris 
sewers were opened, can be easily imagined. Numerous petitions 
were signed, and threats of actions against the Paris munici- 
pality freely hurled, by the inhabitants of the affected suburbs, 
as well as by those interested in the navigation of the Seine, the 
course of which soon became impeded by the deposit of black 
mud along its banks and in its very channel. 
An idea may be formed of the extent to which the river soon 
became polluted by the fact of immense gaseous bubbles, 
several yards in diameter, rising to the surface, then bursting, and 
filling the atmosphere with a most offensive stench. Some of 
the chemists attached to the Paris Sewers Committee had the 
curiosity to analyse the gas which issued from these bubbles ; 
and they found it to consist chiefly of proto-carbonate of hy- 
drogen, burning with a blue flame.* 
In the first instance, the Paris authorities, with the view of 
remedying, to a certain extent, the evils so justly complained 
of, adopted no better expedient than that of constructing huge 
tanks, into which the contents of the sewers were first diverted, 
in order that they might undergo a preliminary purifying process 
previous to their being poured into the river. But these tanks 
were soon found inadequate to the influx of the sewage. 
However, the experiment was tried ; and at first the precipita- 
tion of the solid matter was effected by natural gravitation taking 
place, when the sewage was at rest in the tanks. The com- 
paratively clear liquid was then decanted back into the river, and 
the solid residue removed from the bottom of the tank, which 
was then immediately refilled. But this imperfect method only 
rendered the evil still more crying, inasmuch as no sooner was 
the liquid at rest, than it entered at once into active fermenta- 
tion and decomposition ; and the stench that arose from the 
tanks was most insufferable, especially in the summer months. 
Then purification by means of chemical action was tried. 
Sewage-water contains various mineral and organic matters, 
which impart to it an alkaline reaction, and is thus easily acted 
upon by chemical processes, of which these matters become 
themselves energetic elements. Numerous experiments were 
therefore made with a view to obtain more rapidly and more 
* The exact composition of that gas was as follows : — 
Proto-carbonated hydrogen . . . . 72 • 88 
Carbonic acid 12 '30 
Oxide of carbon 2-54 
Sulphydric acid 6 '70 
Other substances 5 "58 
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