... | ... |
salts }| | | | |
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On examining the tables given above, it is obvious that guanos may be
divided into two classes, the one characterized by the abundance of
ammonia, the other by that of phosphates; and which, for convenience
sake, may be called ammoniacal and phosphatic guanos. Peruvian and
Angamos are characteristic of the former, and Saldanha Bay and Bolivian
of the latter class. The value of these two classes of guano differs
materially, and they are also applicable under different circumstances,
but to these points reference will afterwards be made.

Very special precautions are necessary on the part of the farmer in
order to insure his obtaining a guano which is not adulterated, and of
good quality if genuine. In the case of Peruvian guano, which is
tolerably uniform in its qualities, it is possible to form some opinion
by careful examination, and the following points ought to be attended
to:

1st, The guano should be light coloured. If it is dark, the chances are
that it has been damaged by water.

2d, It should be dry, and when a handful is well squeezed together it
should cohere very slightly.

3d, It should not have too powerful an ammoniacal odour.

4th, It should contain lumps, which, when broken, appear of a paler
colour than the powdery part of the sample.

5th, When rubbed between the fingers it should not be gritty.

6th, A bushel of the guano should not weigh more than from 56 to 60 lbs.

These characters must not, however, be too implicitly relied on, for
they are all imitated with wonderful ingenuity by the skilful
adulterator, and they are applicable only to Peruvian guano; the others
being so variable that no general rules can be given for determining
whether they are genuine. Neither are they so precise as to enable us to
give any opinion regarding the relative values of several samples where
all are genuine. The only way in which adulteration can with certainty
be detected, and the value of different guanos be determined, is by
analysis, and the importance of this can easily be illustrated.

In the table above, the _average_ composition of the different guanos is
given; but in order to shew how much individual cargos may differ from
the mean, we give here analyses of samples of the highest and lowest
quality of the genuine guanos of most importance:

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