GUANO, gwiltnts (Sp. guano, huano, from Peruvian huanu, dung). A name applied to the excrementitious deposits of sea-fowl, such as pelicans, penguins, and gulls, which are found on certain coasts and islands where the climate is dry and the rainfall slight. The deposits some times contain, in addition to excrementitious mat ter, the remains of the birds themselves, as well as of seals, walruses, and various other animals. Although the use of guano as a manure is com paratively recent, dating from about the middle of the nineteenth century, its value in agricul ture was well known to the Peruvians long before they were visited by the Spaniards, probably as early as the twelfth century. Alexander von Humboldt first brought specimens of guano to Europe in 1804, and had them examined by the best analytical chemists of the day. Since then numerous analyses have been reported. TI4most noted deposits of guano are those found in the vicinity of Peru; but valuable beds have been discovered in many other parts of the world— viz. in North America, West Indies, Australia, Asia, Africa, and certain islands of the Pacific. The deposits, however, occur mainly within 10° to 20° north and south of the equator. The qual ity and value of the guano commercially depend almost wholly upon the amount of decomposition to which it has been subjected by the action of the atmosphere. The focal matter of the fish eating birds, which by its long accumulation forms the guano deposits, consists essentially of nitrogenous and phosphatic compounds, the for mer being chiefly ammonia salts and nitrates de rived from the decomposition of the uric acid and urates which exist in the fresh excrements of the birds, as well as of undecomposed or partially decomposed uric acid and urates and other or ganic compounds. The ammoniacal salts and nitrates, and some of the phosphates, are soluble in water, and are readily washed away by rain. In dry climates, where very little rain falls, as in some parts of Bolivia and on the western coasts of South America, the deposit of excreta suffers very little from the action of the atmos phere, and retains nearly the whole of its nitro genous and phosphatic compounds. Guanos, on the
other hand, found in regions where rain falls free ly, lose a great part of their soluble constituents, but remain rich in their less soluble constituents —the phosphates of lime and magnesia. Guanos may, therefore, be divided, according to their composition, into three classes: (1) Those which have suffered little from atmospheric action, and which retain nearly the whole of their original constituents, such as the Angamos and Peruvian guanos; (2) those which have lost a considerable portion of their soluble constituents, such as the Ichaboe, Bolivian, and Chilean guanos; (3) those which have lost nearly all their ammonia, and contain but little more than the earthy phosphates of the animal deposit. Many of these are large ly contaminated with sand. In this class belong the African (executing Ichaboe), West Indian, Kuria Muria, Sombrero, Patagonian, and Shark's Bay guanos.
Aikman classes guanos as nitrogenous and phos phatic, and gives the following data as to the composition of the deposits which were reported as still being worked in 1804: Of the more important deposits of nitrogenous guanos which have been exhausted, Angamos con tained nitrogen 20 per cent., phosphoric acid 5 per cent.; Chincha, nitrogen 14 per cent., phos phoric acid 13 per cent.; Ballestas, 12 per cent. each of nitrogen and phosphoric acid; Macabi, nitrogen 11 per cent., phosphoric acid 12 per cent.; Corcovao, nitrogen 11 per cent, phos phoric acid 15; Independence Bay, nitrogen 7 per cent., phosphoric acid 12. Among the phos phatic deposits now exhausted, but of historical interest, were Maracaibo, or Monks, with 42 per cent. of phosphoric acid; Reza Island and Curs coa, 40 per cent.; Starbuck, 38 per cent.; Fan ning Island and Howland, 34 per cent.; Mejil loves and Lacepede Island, 33 per cent.; Som brero, 32 per cent.; and Jarvis Island, 20 per cent.