above analysis, it need scarcely be
pointed out that bat guano would be a most valuable manure.

A singular point about its composition is, that it has been found to
contain a considerable proportion of its nitrogen (as much as 3 per
cent) in the form of nitrates.

_Pigeon and Fowl Dung._

Pigeon dung is a manure which historically is of great importance. The
dung of pigeons was used as a manure by the ancient Romans; and even in
modern times, more especially in France, it was considered a most
important fertiliser. Despite these facts, pigeon dung is by no means a
rich manure, and its composition compares most unfavourably with that of
the guanos we have just been considering. According to Storer,[200] it
only contains from 1-1/4 to 2-1/2 per cent of nitrogen, and from 1-1/2
to 2 per cent of phosphoric acid, and a little over 1 per cent of
potash.

The dung of poultry is just about as poor, fowl dung containing from .8
to 2 per cent of nitrogen, 1-1/2 to 2 per cent of phosphoric acid, and a
little under 1 per cent of potash; while that of ducks and geese is even
poorer.[201]

From these statements it will be seen that the excrements of pigeons,
hens, and ducks do not form a rich manure. One thing about pigeon dung
which is to be noticed, is the fact that it ferments very quickly.

None of the pseudo-guanos, however rich they may be in manurial
ingredients, can be regarded as equal in their action to the genuine
article, for reasons which we have gone into already when considering
the action of guano.

FOOTNOTES:

[183] Bones, it is true, were in use long before guano; but popular as
they deservedly were, they had not been used, at the time of the
importation of guano, to any very considerable extent.

[184] The total annual imports at present may be taken at under 30,000
tons, whereas in 1855 they amounted to over 200,000 tons. For statistics
on this point the reader is referred to the Appendix, Note I., p. 327.

[185] With regard to the origin of certain guano deposits, which are of
very recent date--_e.g._, _Angamos_ and _Ichaboe_--there can be no doubt
whatever, because we can witness the process of formation still taking
place. It is not so, however, with regard to older deposits, for which
some have been inclined to claim mineral origin. The best proof that
such deposits owe their origin mainly to bird excrements is the
comparatively large quantity of _uric acid_ they contain. On the other
hand,