nt in amount, and has
long been exhausted.

Poorer in quality, but more abundant in quantity, were the deposits
found on the Ichaboe and other islands off the south-west coast of
Africa. These deposits were discovered shortly after the introduction of
Peruvian guano, and for a few years supplied considerable quantities of
valuable manure. The deposits first discovered were soon exhausted, so
that for a number of years Ichaboe guano ceased to be procurable. Fresh
deposits, however, were subsequently found, and considerable quantities
have of late years been used in agriculture.[193] Ichaboe guano is
inferior in value to Peruvian. It exemplifies the influence of small
quantities of rain on guano deposits in impoverishing them in their
nitrogen. In much of the Ichaboe guano imported into this country a
large amount of feathers is found. It also contains an abnormally large
quantity of insoluble matter.

Among the other nitrogenous guanos may be mentioned the Patagonian,
Falkland, and Saldanha Bay. They are, like the Ichaboa, of comparatively
recent origin, and are collected in small quantities after the breeding
season every year.

II.--PHOSPHATIC GUANOS.

Phosphatic guanos, as already pointed out, are similar in origin to
nitrogenous guanos. In their case, however, the nitrogen, alkalies, and
soluble phosphates which they originally contained have been almost
entirely lost by the decomposition of their organic matter and the
action of water.[194] Most of them still contain very small quantities
of nitrogen, amounting to a fraction of a per cent. Of these deposits
there are very many occurring on islands in different parts of the
world. In appearance the guano obtained from them is very different from
nitrogenous guano, being much lighter in colour, and of a fine powdery
nature. It forms a very rich phosphatic guano, containing in many cases
between 70 and 80 per cent of insoluble phosphate of lime. Such guanos
are largely used in the manufacture of high-class superphosphates, by
treating them with sulphuric acid. Being of an insoluble nature, they
are not very suitable for direct application to the soil. Of these
phosphatic guanos the following are the chief--those marked in italics
being still unexhausted:--

1. _Baker_, Jarvis, Howland, Starbuck, Flint, _Enderbury_, _Malden_,
Lacepede, _Browse_, _Huon_, _Chesterfield_, _Sydney_, _Phoenix_,
_Arbrohlos_, _Shark's Bay_, and _Timor_--all found on islands in the
Pac