State of the Seivers and Water Supph/ of Paris. 345 
cade, whicli is surmounted bj a fii-e of glowing coke ; the blue 
flame of the carbonated hydrogen is easily recognised at the tojj 
of the vent, where it mounts and undergoes combustion, instead 
of bubbling up in the fleeting current. 
To sum up these details ; the foul stream which enters the 
sewer of Asnieres to be turned into the Seine at the lowest pos- 
sible point, first encounters the barge with its moveable flood-gate. 
Finding no escape but by the aperture near the bottom, it is 
converted into a scouring torrent, which whirls along all the 
deposits for a distance of 2|- miles. A sort of floating island of 
scum is formed round the boat, from which the grease is col- 
lected for industrial purposes. At the mouth of the Seine the 
stream next encounters a long grating, suspended in mid-channel 
but disconnected with the bottom that the sand may pass freely. 
There it parts with all its floating substances, such as straw, vege- 
tables, or wood, which form a bed (paillasse) on the inclined 
plane, from whence they are removed by drag-rakes. 
Still farther on, a bar is so placed as to form a fall of 13 
inches : the sand is thus arrested, and the bank which it forms 
is continuously removed by the scoops of the steam-drag. The 
hood, with its fire of coke, placed over the fall, attracts and con- 
sumes the noxious gases. 
The solid and gaseous bodies being thus disposed of, nothing 
remains but the fluid, which contains matter in chemical solu- 
tion, and this may properly be turned into the Seine, because 
its purification will soon be accomplished by slow combustion 
under the influence of the atmosphere ; the dark stain caused by 
its admixture will soon be obliterated, and before reaching Passy 
the river Avill have regained all its purity. 
These statements have been chiefly derived from two Reports 
by INI. Mille, published in the Appendix to the ' Annales de 
Vaujours.' For further explanations I am much indebted to the 
excellent models of sewers exhibited, among many others, in the 
French Department of the International Exhibition, as Avell as 
to the courtesy and patience with which the gentlemen in charge 
of these models have answered my inquiries. 
When examining these models, I at the same time saw with 
interest the pipes manufactured by M. Hermann et Compagnie, 
contractors for the Paris waterworks. These pipes are perfectly 
smooth within and without, and uniform from one end to another, 
without any kind of projection. When a joint is to be formed, 
a band of indiarubber is slipped over the ends of two pipes placed 
in juxtaposition. Over this band two iron rings, slightly conical 
in form, lying ready to hand on either pipe, are driven home till 
they almost meet. By this simple but effectual kind of joint, the 
