66 
POPULAR SCIENCE REVIEW. 
sluices emitted into the Thames, and as the Abbey Mills 
Pumping Station is but an ordinary lifting- station, such as in 
the Low-Level lines, of both systems, will be built at the 
requisite intervals when the fall of the sewers becomes too low 
for further continuance, and is moreover not yet in existence, 
we may now, having so far explained the principal engineering 
features of the Northern system, select the Southern Outfall 
works for our concluding observations; for, although the 
Northern Outfall reservoir and works extend over the largest 
area — upwards of twelve acres and a half, whilst the Southern 
occupy about eight acres and a half, — the latter are by far the 
most important and complicated. In the Northern system, all 
that has required lifting has been previously raised, and the 
sewage simply flows like a dirty river into a great pool, the 
larger dimensions of which are determined solely by the larger 
amount of area drained ; and for the reservoir itself there is 
no other necessity than the edict of the Board of Works, that 
the sewage shall be let into the river only for the first two 
hours of ebb. The drains could not be permitted to hold it 
stagnant for the intervening ten hours between the tides, 
and therefore a basin must be made to hold it. When the 
appointed time arrives, the numerous sluice-holes will be 
opened, and the pent-up sewage will rush away. This penning- 
up of the sewage is also the reason for the Southern reservoir ; 
and both reservoirs can of course be artificially emptied of their 
contents whenever arrangements are made for the application 
of the sewage to the land as manure, or for its sale for com- 
mercial purposes. While, however, on the north nature^s 
power — gravitation — does the required work, at the Southern 
Outfall steam comes on duty. The differences of levels in this 
system cause all the sewage of the Southern system to arrive 
at the outfall at some feet in depth below low water. Every 
ounce, every drop, has therefore to be lifted for a height of 20 
feet or more before it can be discharged into the Thames. 
Four large pumping- wells, each 22 feet by 33 feet, receive 
the great arterial sewer, for on this side one large one, 
11 feet 6 inches in diameter, brings the stream of the collec- 
tive three mains from New Cross to the outfall station. 
That solids and refuse — kettles, saucepans, broken pots, and 
the multa alia which are committed to the capacious intestines of 
the London drains — may not pass into the pump, a large iron 
grating is fixed vertically in front of the pit into which the 
sewage first enters before running into the pumping-well. 
Against this grating such heavy and dense materials strike, 
and fall into the pit, from the bottom of which buckets 
affixed to a revolving strap scoop the sullage out, and 
convey it to the surface, where, turning over in their 
