THomson.—On the Cleansing of Towns. 48 
14i square miles, forming the western suburb of London, which is so low 
that its sewage has to be lifted at Chelsea a height of 174 feet into the 
upper end of the low level sewer. It is tunnelled under the river Lea, on 
its route to Abbey Mills, where its contents are raised 86 feet by steam 
power. 
Again: “The northern outfall sewer is a work of peculiar construction; 
as, unlike ordinary sewers, it is raised above the level of the surrounding 
neighbourhood in an embankment, which has the appearance of a railway 
embankment, and it is carried by aqueducts over rivers, railways, streets 
and roads.” 
Again: “The Barking reservoir is 163 feet in average depth, and is 
divided by partition walls into four compartments, covering altogether an 
effective area of 412,384 superficial feet, or about 9434 acres. The external 
and partition walls are of brickwork, and the centre area is covered by 
brick arches supported upon brick piers, the floor being paved throughout 
with York stone. The reservoir, being almost entirely above the general 
surface of the ground, is covered by an embankment of earth, rising about 
2 feet above the crown of the arches. The ground over which it is built 
being unfit to sustain the structure, the foundations of the piers, and of the 
walls, were carried down in concrete to a depth of nearly 20 feet.” 
Again: ** The Abbey Mills Pumping Station will be the largest establish- 
ment of the kind in the main drainage works, providing, as it does, engine- 
power to the extent of 1140 h.p. for the purpose of lifting a minimum 
quantity of sewage and rainfall of 15,000 cubic feet per minute a height 
of 36 feet." 
The Engineer adds that “It is fortunate that these works were not 
projected in the year 1806 when coal was first introduced into London, 
and was regarded as such a nuisance that the resident nobility obtained a 
royal proclamation to prohibit its use under severe penalties; for this 
pumping station alone will consume about 9700 tons of coal per annum. 
The cost of pumping is not, however, actually in excess of the former 
expenditure upon drainage, for the cost of removing deposit from the tide- 
locked and stagnated sewers in London, formerly amounted to a sum of 
about £30,000 per annum, and the substitution of a constant flow through 
sewers by means of pumping must necessarily reduce the deposit, and 
consequently the annual cost of cleaning." 
Again: ‘On the south side of the Thames the high-level sewer and its 
southern braneh correspond with the high and middle-level sewers on the 
north side of the Thames." ‘‘ Both lines are constructed of sufficient 
capacity to carry off the flood waters, so that they may be entirely inter- 
