58 POPULAR SCIENCE REVIEW. 
tlie whole region, there are no less than six chief lines of 
sewers ; or, rather, there are two distinct drainage works, of 
three main lines each ; one system draining all the districts on 
the north side of the Thames, the other all those on the south 
side of the river. 
The northern system consists of a high level, a middle 
level, and a low level main drain ; the southern system of a 
high level, a low level, and the Effra main drain. 
The Northern High Level main, consisting of a brick culvert, 
varying from 4 feet in diameter to 9J feet, starts from Hamp- 
stead at an elevation of 154 feet, and passes through Kentish 
Town, Holloway, Stoke Newington, Clapton, Hackney, and 
Homerton, with an incline of 132 feet in a length of nine miles, 
to the Old Ford over the Lea at Bow, where the Northern 
Outfall sewers commence that carry on the sewage of the main 
drains to the exit into the Thames at Barking’ Creek. The 
Northern Middle Level sewer, which is of brick, and of like 
dimensions, starts from the cemetery at Kensal Green, passing 
through Notting Hill along the Uxbridge Road, intercepting 
the Ranelagh sewer which brings the drainage from Hamp- 
stead and Kilburn at the Gloucester Road, continues along 
the Uxbridge Road to Oxford Street, where it intercepts the 
King's Scholars' Pond sewer at Duke Street, and thence along 
Oxford Street, intercepting the Regent's Park Tunnel sewer 
at Regent's Circus.' At this point there is a weir and overflow 
chamber, to allow the storm- water to pass over and flow down 
the old sewer-course. The Middle Level sewer then passes 
along New Oxford Street, Hart Street, Theobald's Road, 
Liquorpond Street, Bedford Row, to Victoria Street, Clerken- 
well, where it crosses, by means of an iron culvert, over the 
underground railway near the Farringdon Street terminus. 
Here also it intercepts the Fleet sewer, and then goes on 
through Old Street, across Shoreditch, along Bethnal Green 
Road, to the junction of the High Level and Outfall sewers at 
Old Ford. This sewer with its branches runs over twelve miles 
and a half in length, the head from which it starts being 64 
feet above the Trinity datum line. Both these sewers flow 
the whole distance, from their origins to their terminations, by 
gravitation. 
The Northern Low Level sew*er commences at 6 inches 
above Trinity datum at Hammersmith, about a mile west of 
the bridge ; another branch coming from Acton, and a short 
branch through Fulham from Putney Bridge. The sewage 
thence will flow to a pumping- station at Pimlico, where it 
will be lifted from 17 feet below the datum. After the 
junction its course will lie — for this portion is not yet con- 
structed — through Chelsea, close to the river, past the Hospital* 
