MECHANICS AND USEFUL ARTS. 51 



ways into the water. These floating tulics, slightly raised in form 

 at each end, but raised higher on the side of the sewerage en- 

 trance than at the other end, were then wheeled round over the 

 spot where they were to be sunk. Preparatory to tliis, a bed had 

 been duo^ out at about 10 feet below the bed of the river and filled 

 in with concrete. On this bed the two syphons are to rest, then 

 to be covered with concrete flush with the bed of the Seine. 

 They were first loaded with about 1,200 tons of pig iron, and not 

 being sufficiently " stiif " in position they capsized and dropped 

 the pig iron into the river. They have now, however, placed 

 heavy timber to prevent a recurrence of this, and in the course 

 of a day or two these enormous tubes are expected to lie quiBtl}^ 

 side by side, in the placid stream, and do their part in purifying 

 its waters within the boundaries of Paris, as all this sewerage is 

 carried under the city and pours into the river at Asnieres, about 

 14 miles below the city. 



THE CHICAGO-RIVER TUNNEL. 



Work on the Washington-Street tunnel is rapidly progressing, 

 and there is little doubt that this great thoroughfare may be 

 opened in the early spring. The obstructions are to be removed, 

 from the river by December!. Six hundred and sixty-five feet 

 of the arching are already finished, leaving 265 feet still to be 

 built. The east excavation is now 80 feet inside the river-bed. 

 On the west side the excavations arc within 25 feet of the river. 

 The general plan of the tunnel is already known. 



Single passages, for horse and foot separately, are built to the 

 water's edge, where the passage is doubled for the carriage-way, 

 extending 220 feet, one side forgoing east, and the other side for 

 the west, thus preventing any danger of collision. The foot-path 

 is 6 feet above the carriage-road, in the middle of the tunnel. 

 When all the arches are completed, the top is to be covered with 

 masonry, making all level ; over this will be a coating of govern- 

 ment asphaltum, poured on hot, and thus running into and filling 

 all the seams, and forming a water-tight sheeting ; over this 

 again, large, heavy flag-stones, of the usual white stone, are to 

 be laid, and the joints filled with asphaltum. Then the water is 

 allowed to flovv over all. Between each course of brick in the 

 arches is a half inch of cement. Beneath the centre of the pas- 

 sage-way, under foot, is a sewer 120 feet long, — over 100 feet of 

 which is now built, — leading to a well in the centre of the tunnel 

 bottom, into which all water accumulating in the tunnel flows, 

 and is pumped up by a powerful engine to the surface and back 

 to the river. The cost of the tunnel for material and labor is 

 about $8,000 per week. The original contract was $328,500, but 

 the actual cost will not be less than $500,000. — Chicago Post. 



The whole length of the work from the centre of Franklin Street 

 to the centre of Clinton Street is 1,G05 feet, of which 932 feet is the 

 length of the tunnel; the remainder consists of the open ap- 

 proaches. Opened to the public Jan. 1, 1869. 



