Guano , (Sp. guano or huano, Peruvian huanu, dung), the excrement of sea fowl, intermixed with their decomposed bodies and eggs, and the remains of seals, found accumulated principally upon the islands of the Pacific and coasts of South America and Africa. The three small islands called the Chincha islands, off the south coast of Peru, and the Lobos islands off the north coast, were covered with it. It was known to the ancient Peruvians as a valuable manure, and the immense deposits of it were an especial object of care to the incas. Acosta (quoted by Prescott) states that during the breeding season no one was allowed under pain of death to set foot on the islands on which it was produced, and to kill the birds at any time was a like offence. The Spanish conquerors called the islands the Sierra Nevada, or snowy mountains, from the hills covered with white saline incrustation. Humboldt first drew attention in Europe to the substance in 1804. He described the deposits as covering the granitic rocks of the Chincha islands to the depth of 50 or GO ft:, and yet the accumulation of the preceding 300 years had formed only a few lines of this thickness.
He procured analyses to be made of the substance by Foureroy, Vauquelin, and Klaproth, by which it was found to be composed of phosphate of ammonia and lime, with urate and oxalate of ammonia, water, organic matters not determined, and some sand. Sir Humphry Davy alluded to it about 1810 as likely to prove valuable to European farmers; and in that year a trial was made of it at St. Helena by Gen. Beatson. But none was brought to Europe for trial till 1840, when 20 casks were imported into Liverpool by Mr. Myers. The next year the shipments amounted to several cargoes. The exclusive right of digging and shipping guano for the term of nine years was sold at this time by the Peruvian and Bolivian governments for the sum of $40,000; but the contract was soon after repudiated by the former, as the increasing demand for the article developed the immense value of the deposits. The monopoly was soon after revived, however, the Peruvian government confining the exportation and sale to a single house in London and another in New York. Upon the Chincha islands it was estimated that there were about 40,000,000 tons, the largest one having no less than 17,000,000 tons. The Lobos islands also contained enormous deposits, and many smaller islands were covered with it.
Upon the principal Chincha island the deposit is said to attain a thickness of 100 ft. The exports from these localities rapidly increased, so that guano became an important article of commerce, and vessels returning from the Pacific to England or the United States now found a profitable return cargo at the Chincha islands, instead of going as they had previously done to China and the East Indies in search of one. The revenue to the Peruvian government from this trade exceeded that from all other sources; and its agents reaped enormous profits from their authorized commissions upon the shipments. The demand led to explorations in other parts of the world, and other deposits were found, but nearly all inferior in quality to those collected upon the | rainless islands off the coast of Peru. Upon these the ingredients have remained little changed in the dry atmosphere and under the tropical sun. The uric acid and ammonia, both products particularly subject to ferment and decompose in the presence of moisture, remain unaltered, except as they become dry and are locked up in the coarse brown powder produced from these and the other ingredients of the excrement.
So the nitrate of soda and common salt, both deliquescent in a moist atmosphere, are found as a dry deposit among the parched sands of the desert of Atacama in the same rainless district. In localities subject to rains these valuable nitrogenous compounds disappear, and the value of the guano consists principally in the next useful ingredients, the phosphates, which remain. The greater portion of the guano product of Peru is sent to England. The entire imports into Great Britain amounted in 1870 to 280,311 tons, valued at £3,470,680; in 1871, 178,808 tons, valued at £1,986,989; and in 1872, 118,704 tons, valued at £1,201,042. Of the imports in 1872, 74,401 tons, valued at £875,882, came from Peru; 17,475 tons, worth £113,073, from the islands in the Pacific; and 14,068 tons, worth £108,-150, from Bolivia. During the year ending June 30, 1872, there was imported into the United States 14,309 tons of guano, valued at $423,323, of which 11,654 tons, worth $385,-063, were from Peru, and 1,820 tons, worth $24,473, from the British West Indies. Besides this amount, 4,209 tons, valued at $60,865, were from the islands, rocks, and keys belonging to the United States. - The composition of guano is exceedingly complex.
The following minute analyses of South American samples were communicated by J. Denham Smith to the chemical society, and published in vol. ii. of their "Memoirs." Nos. 1 and 2 were in the state of powder; the others were of the concrete variety:
Soluble in cold water.
Muriate of ammonia
Sulphate of soda....
Oxalate of ammonia
Oxalate of soda.....
Phos. of ammonia..
Phosphate of lime..
Phosphate of potash
Phosphate of soda..
Chlor. of potassium
■ . . .
Chloride of sodium.
Soluble in boiling water.
Urate of ammonia .
Phos. am. and mag.
Phosphate of soda..
• • • •
Phosphate of lime..
Organic matter ....
Insoluble in water.
Oxalate of lime___
Phosphate of lime..
Phos. of magnesia..
Ox. iron and alum a
The following are forms and examples of ordinary commercial analyses:
Org. matter and ammon'al salts.
Sulphate of lime................
Carbonate of lime..............
Phosphoric acid in alkaline salts.
For commercial purposes it is of no impor- tance to enumerate all the compounds. The approximate value of samples can be arrived at in the following manner: Multiply the values named below by the per cent. found of each ingredient; the sum obtained will represent the value of 100 tons of the guano. Thus for the nitrogen found the rate per cent. is $370, or if, instead of this being separated, the ammonia is estimated, the rate is $300; for phosphate of lime the additional amount is $4<); soluble phosphate of lime, $120; organic matter, $5; alkaline salts, $5; sulphate of lime, $5. Example of sample of first-class Peruvian guano:
Phosphate of lime.....
Soluble phosphate of lime, equivalent to the phosphoric acid above...
Ammonia derivable from the organic matter above....
300 = .
Value of 100 tons....
Org. matter and ammon'l salts
Sulph. of lime.
Soluble salts ..
Sulph. of lime.
Phos. of lime..
Carbs. & silica
Analyses and calculations like those given ought to be made in entering upon all large purchases of guano, as well on account of the great natural differences in the qualities of the various kinds, even from the same locality, as of the gross adulterations which are largely and most ingeniously practised; substances of no value as fertilizers being intermixed with the genuine article, so as to very materially reduce its value. Full half the guano sold in England is said to be thus deteriorated. The analyses, moreover, are of importance, as they indicate the most advantageous methods of applying the guanos, and for what crops and what soils they are best adapted. But for the knowledge of their composition thus acquired, the best Peruvian guano, rich in ammonia, might be extravagantly employed upon soils that would be almost equally benefited by the cheaper qualities, of which the phosphates are the chief fertilizing ingredients. Upon light soils especially, the ammoniacal guano may be used to waste, owing to the little obstruction they present to the escape of its volatile and very soluble portions; the full benefit of these will be secured only in the strongest soils, or in composts prepared with the view of their absorption and retention. In such mixtures guano is used most advantageously.
Of itself alone it may furnish all the ingredients required by the plants; but its activity and evanescence need to be checked, and on account of its caustic quality care should be taken that it be not brought in direct contact with the seed. The quantity of best guano that should be employed to the acre is generally rated at from 3 to 5 cwt.; and it should be applied in wet weather, when the rains diffuse it equally through the soil. The Peruvians, it is said, irrigate immediately after applying it. They use it only for Indian corn and potatoes, burying about half a handful near each root when the plants are perhaps half grown, and adding some water "to fix the guano." In this country it is found to be an excellent top dressing for grass and young corn, and is a most efficient manure for all the root crops. - The search for new localities of guano led to the discovery in 1855 of animal deposits of the same original nature upon the groups of islands lying off the coast of Guiana and Venezuela. Immense flocks of sea fowl frequent these islands for the purpose of laying their eggs.
But being in the region of the tropical rains, the deposits of excrement and other organic matters are subject to chemical changes, from which result singular products, very different from those of the earthy guano of the dry islands of the Pacific. The principal groups which furnish these products are Los Monges (Monks' island), El Roque, and Centi-nella. Some of the islands are low, and strewed with sand, which is made up of comminuted coral, madrepore, and shells, in which the birds lay their eggs. Others rise in peaks to the height of 800 ft., and upon these are stratified rocky layers of metamorphic guano, sometimes covered with the deposits still in process of accumulation. Several qualities of guano are recognized, one of which is arenaceous, in grains as coarse as mustard seed, light yellowish brown or nearly white when dried, exhaling an odor not ammoniacal, but like that of freshly dug earth. Its average composition is thus stated by Dr. A. A. Hayes: moisture, after drying, 4.40; organic matter, 6.40; bone phosphate of lime, 46.60; carbonate of lime, 39.80; phosphate of magnesia, 1.20; sulphate of lime, 0.80; sand, 0.21; traces of chloride and sulphate of soda; total, 99.41. The ammonia or nitrogen in the organic matters does not exceed 2 per cent. of the whole.
Another variety is in aggregated grains, the first step in the change of the material into rock. It differs in composition from the preceding principally by loss of carbonate of lime and increased proportion of bone phosphate. A third variety is a solid rock, which forms a crust sometimes 2 ft. thick over the lower portions of the deposit, and is the product of the change that has taken place upon the surface of the mass. Its composition is somewhat variable at different localities; but it is everywhere distinguished by the disappearance of carbonate of lime and large increase in the proportion of phosphate and sulphate of lime. The carbonate of lime has been decomposed by the acids generated in the fermentation induced by the moisture at the prevailing elevated temperature, and with other soluble matters has been removed by the rains. The passage of the gaseous exhalations through the mass, gradually thickening as its aqueous portion evaporates and the salts gather at the surface, renders its structure porous and cellular, and so much like that of some trachytic rocks that the substance has been mistaken for one of igneous origin, or at least metamorphosed by heat.
The granular structure has given place to a compact, close texture, and a mineral appearance and hardness closely approaching that of feldspar; and in some specimens are observed angular fragments and grains hardly to be distinguished by the eye from epidote. The external surface has an uneven weathered appearance like that of trap rock, and is of a lighter color than the body of the rock within. Various analyses have been made of this substance by different chemists, and it is found to consist principally of phosphoric acid and lime, the former generally ranging from 37 to 46 per cent., and the latter from 39 to 41 per cent., of which a small portion is combined with sulphuric acid to form sulphate of lime, the proportion of this sometimes exceeding 8 per cent., and the crystals being visible in the cells of the mineral. Water and organic matters sometimes exceed 10 per cent. In the body of the rock the phosphoric acid is found combined with two atoms of base and one of water, in the form of common phosphate of lime; while the external part is a combination of an atom of acid with three of lime, forming the so-called tri-phosphate of lime. The acid is also sometimes combined in small proportion with iron, alumina, and magnesia.
Soda is present in some samples to the amount of 2 or 3 per cent. Much of the guano rock closely resembles in appearance the phosphate of lime rocks of the older crystalline formations; and it affords a remarkable instance of the conversion of modern collections of organic substances into what appears to be an ancient rock. Though traced directly into the mass of these substances with which it is associated, and the derivation of which is obviously from the digested bones of fishes and other food of birds, from comminuted shells, and the remains of the birds themselves and of their eggs, all vestiges of animal life have as completely disappeared in the hard strata as they have from the true metamorphic rocks, the changes in which we have been accustomed to ascribe to intense heat produced under the pressure of superincumbent mountains of rock, and exerted through long and indefinite periods.