n a more or less
completely decomposed state, and is accumulated in immense quantities on
the coasts of South America and other tropical countries. It has been
used as a manure in Peru from time immemorial, but the accounts given by
the older travellers of its marvellous effects were considered to be
fabulous, until Humboldt, from personal observation, confirmed their
statements. It was first imported into this country in 1840, in which
year a few barrels of it were brought home; and from that time its
importation rapidly increased. Soon after large deposits of it were
found in Ichaboe; and it has since been brought from many other
localities. The quantity of guanos of all kinds imported into this
country and retained for home consumption now exceeds 240,000 tons a
year.

The value of guano differs greatly according to the extent to which its
decomposition has gone, and this is chiefly dependent on the climate of
the locality from which it is obtained. When deposited in the rainless
districts of Peru it still retains some of the uric acid and the greater
part of the ammonia naturally existing in it, and the quantity which has
escaped by decomposition is unimportant. But that obtained from other
districts has suffered a more or less complete decomposition according
to the humidity of the climate, which reduces the quantity of organic
matters and ammonia, until, in some varieties, they are so small as to
be of little importance. The following are minute analyses of three
specimens of Peruvian guano, shewing all the different constituents it
contains, and the amount of difference which may exist:--

I. II. III.
Urate of ammonia 10.70 9.0 3.24
Oxalate of ammonia 12.38 10.6 13.35
Oxalate of lime 5.44 7.0 16.36
Phosphate of ammonia 19.25 6.0 6.45
Phosphate of magnesia and ammonia ... 2.6 4.20
Sulphate of potash 4.50 5.5 4.23
Sulphate of soda 1.95 3.8 1.12
Sulphate of ammonia 3.36 ... ...
Muriate of ammonia 4.81 4.2 6.50
Phosphate of soda ... ... 5.29
Chloride of sodium ... ... 0.10
Phosphate of lime 15.56 14.3 9.94
Carbonate of lime 1.80 ... ...
Sand and alumina