16 ANNUAL OF SCIENTIFIC DISCOVERY. 



general collector. After much reflection, It was decided that the waters 

 of the left bank should be carried over by a siphon passing under the 

 bed of the Seine ; and this singular engineering feat has actually been 

 accomplished. An enormous pipe of wrought iron having an interior 

 diameter of one metre, and about 200 metres in length, is sunk, a little 

 above the Pont de la Concorde, two metres below the low-water mark, 

 and thus the desired communication is established. As to the general 

 collector, it is the most stupendous work of the kind in existence. It 

 is 5 metres in height by 5.G1 in breadth, with a length of about five 

 kilometres and a half, in nearly a right line, except a turn under the 

 Place de la Madeleine. The foot pavements are 1.90 metres on each 

 side, the central drain is 3.60 metres in breadth, with a depth of 1.35 ; 

 so large, in fact, that a well sized boat is kept afloat on it for the pur- 

 pose of cleansing. This boat is also provided with a drop-plank in 

 front; this is let down to a distance of 15 centimetres from the bottom, 

 while the boat advances, whereby such a head of water is obtained in 

 front as to drive all the sedimentary matter nay, even stones to a 

 distance of 100 metres. There the boat finds it again as it advances, 

 and drives it further and further, till the orifice of the emissary is 

 reached. Four boats perform this work, and it takes sixteen days to 

 cleanse the whole length. Ventilation is provided for by air-traps at 

 certain distances, and the gallery is lighted with oil lamps. The exe- 

 cution of this immense system of sewers has cost fifty millions of francs. 

 M. Dezobry, comparing this gallery with the far-famed Cloaca Maxima 

 of Rome, shows that it is infinitely superior to it in size, not to mention 

 the improvements in construction, of which the Romans had no idea. 

 The Cloaca Maxima is two metres in height, and only 4.48 broad, and 

 is supposed never to have exceeded a length of 900 metres. The di- 

 mensions we have given abundantly show how vastly superior the 

 modern French construction is to the ancient Roman one. 



THE NEW SEWERS OF LONDON. 



It is well known to our readers (See Annual Sci. Dis., 1859-60) 

 that for the last few years, there has been in the course of construction 

 in London, a system of sewage, of such magnitude as to form one of 

 the marvels of modern engineering, and of such cost, as but few cities 

 could afford to pay for. The. object of the scheme is to do away with 

 the present plan, whereby all the enormous drainage of London is dis- 

 charged into the Thames; a plan which has latterly converted the 

 river itself into one vast sewer, to the great annoyance and sanitary 

 detriment of the vast population contiguous to its waters. " At the very 

 first glance," says the London Times : " This arrangement seems bad 

 enough, though it is infinitely worse when we come to examine how it 

 was arranged to work. On both sides of the river the banks are very 

 little above high-water mark, while the average level of the ground im- 

 mediately behind them is much below it ; half Lambeth and Rothcr- 

 hithc being six feet below high-water level. Of course, when this is the 

 level of the ground, the sewers arc much lower still, and their outlets so 

 completely tide-locked that it is only at dead low-water that they can 

 empty themselves at all. Thus, for nearly eighteen hours out of the 

 twenty-four, the sewage on both sides of London is to an immense ex- 

 tent, pent up, giving off its miasma into every street and house. As 



