Composition and Practical Value of Native Guano. 
All 
mixture for 1000 f^^allons of sewage. "The sewage must then be 
thoroughly mixed with the compound and allowed to flow into the 
settling tanks. The greater part of the organic and other impurities 
will be immediately separated in the form of large Hakes, which 
rapidly fall to the bottom, leaving the supernatant water clear 
and inodorous, or nearly so. The matter may then be allowed to 
accumulate at the bottom of the tank. In some cases it is pre- 
ferable to add the compound of manganese to the water after the 
sediment produced by the other ingredients has been allowed to 
subside. The sediment will be found to possess the power 
of precipitating a further quantity of sewage ; it must therefore 
be pumped or otherwise taken from the tank and mixed with 
fresh sewage, the sediment being allowed to subside in the same 
way as before. The sediment may be used 5 or 6 times in this 
way. When the sediment no longer possesses the power of pre- 
cipitating the impurities of sewage, it must be removed from the 
tank and allowed to dry ; when partially dry a small quantity of 
acid, by preference sulphuric acid, may be mixed with it, which 
will retain all the ammonia in a soluble form. When dried, the 
sediment will be a valuable manure." 
It will be noticed that besides alum (A), blood (B), and clay 
(C) — ingredients suggestive of the name of the ABC process — 
a large number of other substances are included in the preceding 
list of chemical agents, which may be employed in the treatment 
of sewage by the process. The use of alum for the purpose of 
clarifying foul water has been known from time immemorial, 
and found efficacious in precipitating more or less perfectly the 
nitrogenous or albumenoid compounds which are present in 
sewage and similar refuse liquids. Town sewage has always 
an alkaline reaction, and yields with a weak solution of alum an 
abundant flocculent precipitate. There is therefore no need to 
introduce into sewage nitrogenous or albuminous matters in the 
the shape of blood, with a view of causing a flaky precipitate, 
which, like coagulated white of eggs, will carry down with it 
suspended impurities, and thereby effect the clarification of the 
muddy liquid. The patentees, therefore, are wise in giving 
only the faintest sprinkling of blood to their precipitating mixture. 
If they omitted the blood altogether, the manure which they 
abstract from sewage, other conditions being equal, practically 
would be neither the worse nor the better for this omission, nor 
would the purification of the effluent sewage be less complete. 
Why 10 parts of chloride of sodium should be mentioned as 
one of the ingredients in the preceding mixture is difficult to 
comprehend, for, being a very soluble salt it will, of course, 
pass off W'ith the effluent water, and in the proportion in 
which it is employed in the purifying mixture the salt cannot 
