142 TOWN SEWAGE, AND ITS APPLICATION TO AGPJCULTURE. 



the whole of the solid impurities, and a good deal of the 

 dissolved substances are carried down in the form of clots and 

 flocks, and the supernatant liquid is sufficiently purified to run 

 into any river. This is fully evinced by the local authorities, 

 and by a large number of scientific witnesses who were examined 

 before the Privy Council, as well as by the thriving state of the 

 fish in the defecated water. 



The fertilising power of sewage when not overpowered with 

 water is unquestionable, and the dried mud obtained by the 

 purifying process would probably be threefold its actual 

 manurial value but for the A. B. C. materials which constitute so 

 large a part of its weight. This fact explains the reason why 

 the dry product does not show well when tested by chemical 

 analysis ; but the good practical evidence of its value when 

 applied in quantity is proved by many testimonials of gardeners 

 and farmers who have been using it. The early estimates of 

 the value of sewage were greatly exaggerated, but when it is 

 considered that a gallon weighs a little over 10 lbs,, and that 

 there are only 60 to 100 grains of manurial matter in the gallon 

 (7000 grains to the pound), we arrive at sounder views as to the 

 value of sewage, and the enormous amount of w^ater with which 

 the manure is diluted. The liquid excreta of man, it may be 

 stated, has a high manurial value, and as the A. B. C. process 

 does not extract or precipitate all the manures in solution, 

 doubtless the comparatively low fertilising power of the " native 

 guano " is partly owing to that circumstance. 



During an official trial on the purification of London sewage 

 by the A. B. C. process, there were used 80 tons of dry A. B. C. 

 materials, whilst the " native guano " obtained amounted in a 

 dry state to 131 tons, showing an increase of more than 63 per 

 cent. The amount of sewage treated during this time was 

 11,672,000 gallons. Therefore one ton of dry guano was 

 obtained from 89,100 gallons of London sewage. The quantity 

 of materials required to purify sewage depends upon the 

 character of the water, as well as upon the proportions of those 

 ingredients. For the nature, too, of the manufacturing refuse of 

 towns, the proportions of those ingredients have to be altered, 

 ^s we have already said, farmers speak highly of the applica- 

 tion of this native guano to all crops. The quantities used for 

 the acre are very much the same as the cost of other artificial 

 manures. For wheat a dressing of from 4 to 8 cwt. is put on 

 the acre in autumn, and oats and barley get 6 to 10 cwt. at the 

 time of sowing. For turnips, swedes, and mangels, 8 to 12 cwt. 

 per acre, in row or broadcast, is applied to the acre. 



