the evidence in support of the belief that they are also formed
from the remains of the birds themselves and other animals, is to be
found in the large proportion of phosphates they contain, and the
presence in the deposits of feathers and the fossilised skeletons of the
animals above mentioned.

[186] A complete list of the various deposits will be found in the
Appendix, Note II., p. 327. It may be noticed that nearly all the
deposits lie within 10 deg. to 20 deg. north and south of the Equator.

[187] See Chapter on Farmyard Manure, p. 257.

[188] According to Nesbit, some of the cargoes of this guano contained
hard saline lumps of very little manurial value--over 50 per cent being
common salt.

[189] The salt exports were made in 1868.

[190] For analyses of these nodules and crystals, see Appendix, Note
III., p. 328.

[191] See Heiden, vol. ii. p. 356.

[192] See Appendix, Note IV., p. 329.

[193] The Ichaboe guano at present exported is a fresh deposit, and is
annually collected for shipment.

[194] Further chemical changes have occurred in certain cases between
the guano and the limestone rock beneath, resulting in the formation of
what is called a "crust" guano. Such guanos form a soft phosphatic rock,
and are extremely rich in phosphates. As examples of these "crust"
guanos may be mentioned Sombrero, Curacao, Aruba, Mexico, and Navassa
phosphates.

[195] The presence in the old Peruvian guano of concretionary nodules
has already been referred to.

[196] According to Vogel the nitrogen as urates is converted by the
sulphuric acid into ammonia salts.

[197] See Appendix, Note VI. p. 330.

[198] It must be remembered, however, that even genuine guano contains a
certain quantity of carbonate of lime, and will give a slight amount of
effervescence when so treated.

[199] The annual imports may be stated at from 3000 to 4000 tons.

[200] Agricultural Chemistry, vol. i. p. 367.

[201] See Appendix, Note VII., p. 331.

APPENDIX TO CHAPTER VIII.

NOTE I. (p. 297).

PERUVIAN GUANO IMPORTED INTO THE UNITED KINGDOM, 1865-1893.

Year. Tons. | Year. Tons.
1865 213,024 | 1881 33,393
1870 247,028 | 1882 27,382
1871 144,735 | 1883 36,713
1872 74,964 | 1884 15,802
1873 135,895 | 1885 -
1874 94,346 | 1886 28,733
1875 86,042 | 1887