28 ox THE DISPOS.U. OF SEWAGE. 



54 lbs. each at a time, a bag of slaked lime being added to each 

 lot. The sludge-cakes are sold as a manure at Is. 6d. per ton. 

 In 1885, when I visited Chiswick, the population was 20,000, 

 and it cost £1,200 a-year to treat the sewage, so as to secure 

 a good effluent. The cost of pressing the sludge \vas £380 

 additional. The press treated from forty-live to fifty tons of wet 

 sludge per day. The engine and presses cost £900. A Latham's 

 extractor was used to remove tlie larger suspended matters, the 

 cost of which, with engine complete, being £400. The sewers 

 were Hushed with iiutomatic flushing tanks at a cost of £3o0 

 a-year — Field's, Adams's, or Doulton's being used. The effluent 

 must be of a tolerable standard of purity, as a number of water 

 companies have their intake from the Thames some miles above 

 Chiswick, viz., at Hampton, Ditton, Kew, and Sunbury, and one 

 company — the West Middlesex — has a pumping station at 

 Hammersmith, which is about two miles lower down the river 

 from Chiswick. 



A i)rocess of somewhat recent origin termed the Ferozone 

 and Polarite Process, is said to yield very satisfactory results. 

 In this the introduction of the precipitating material termed 

 " ferozone" is followed by the filtration of the effluent through 

 a filter containing polarite. Professor Roscoe gives the follow- 

 analysis of ferozone : — 



Ferrous sulphate . . . . . . "2(5. (54 



Aluniiniuiu sulphate . . . . . . 2. lit 



Calcium sulphate . . . . . . 8.80 



MaKuesium sulphate .. .. .. o.l? 



Combined water . . . . . . 8.20 



Moisture .. .. .. .. 24.14 



Silica .. .. .. .. 11.3.5 



Magnetic oxide of iron ... .. .. IS). 01 



100.00 

 Professor Roscoe gives the analysis of polarite as — 



Magnetic oxide of iron . . . . . . 58.85 



Alumina . . . . . . . . 5.68 



Magnesia .. ... .. .. 7.55 



Water, with a trace of carbon . . . . .5.41 



Sihca . . . . . . . . 25.50 



Lime . . . . . . . . 2.01 



100.00 



