THE 



ANNUAL Or SCIENTIFIC DISCOVERT. 



MECHANICS AND USEFUL ARTS. 



THE SEWERS OF PARIS. 



THE present system of sewerage in Paris, decreed by the Emperor 

 Napoleon III. in 1852, consists of six main galleries, called collectors, 

 fifteen secondary ones opening into the former, and themselves fed by 

 a vast number of smaller ones intersecting the city in every direction. 

 Three of the collectors are located upon the right bank of the Seine, 

 and three upon the left bank. The united length of the former is 

 8.GOO metres; of the latter, 9.200 metres. 



The ratio of the section to be given to the various sewers has been 

 fixed, as experience required, at from two to three square metres of 

 wet surface for every 100 hectares. On this principle, twelve different 

 sizes have been chosen, the smallest having a section of 2.15 metres in 

 height by 1.15 in breadth, and the largest one of 4.40 metres in height 

 by 5. GO in breadth. The former is of an ovoid shape, and offers ample 

 space for a man and a wheelbarrow. The largest sewer or collector 

 has a circular segment for its section ; its breadth is divided into three 

 parts, the two lateral ones being foot pavements, and the middle one a 

 gutter or drain 1.20 metres broad. On each foot pavement, a series of 

 iron forks support a water pipe, varying in diameter from 1.10 metres 

 to 0.80. In some of the galleries there is but one water-pipe. To 

 cleanse the drain a small cart, running on iron rails laid along the bot- 

 tom, is pushed forward by two men ; the front of this cart is provided 

 with a drop-plank, acting like a sort of sluice, which, when down, 

 exactly closes the section of the gutter, and pushes all the mud before 

 it as the cart advances. By the sewers above described, all the foul 

 waters of the right bank are easily brought to the Place de la Con- 

 corde, where a general collector receives them and carries them off to 

 Asrueres. But what was to be done with the sewerage of the left bank, 

 which, according to the system adopted, was also to be poured into the 



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