NITROGENIZED PHOSPHATIC MANURES. 279 



according to the situation of the ditferent deposits The most 

 esteemed kind was that formerly collected on the Chmcha Isles, 

 well known to the ancient Peruvians, who came there to search tor 

 manure to fertilize their wheat and potato fields. But these islands 

 are now completely exhausted, as well as those of Ballestas, Guanape 

 and Macabi. It is, therefore, unnecessary to describe them How- 

 ever, we cannot help quoting the analyses of the samples of guano 

 brought from these islands by Alexander de Humboldt m 1804, and 

 of some others because they correspond near enough with the guanos 

 now imported from these countries (see p. 280). The following are 

 some of the distinctive characters of Peruvian guano, according to 



J. Girardin : — ^ 7 v i 1.,.+ u 



It is a dry powder of a pale yellow or caje au lait colour, but it 

 becomes chocolate as it ages or when it is exposed to the air ; it 

 absorbs, moreover, in the latter case much moisture, becomes 

 heavier and sticks to the fingers. It exhales a strong putrid or 

 ammoniacal odour which induces sneezing. It has a very siiaip 

 salt taste. It shows in bulk numerous whitish semi-hard concre- 

 tions which can be crushed between the fingers, and which when 

 exposed to the air soon slake and fall to dust exhaling a very strong 

 animoniacal odour. Thrown into water, Peruvian guano soon hnds 

 the bottom and lets nothing rise ; when heated it blackens burning 

 with a feeble flame with production of a strong ammoniacal vapour ; 

 the residue which it leaves is in the form of a white s ightly bluish 

 cavernous slag ; the weight of this residue only varies between very 

 near limits, 27-5 to 35 per cent. _ • ^• 



Triturated with powdered quicklime, Peruvian guano immedi- 

 ately gives off a strong ammoniacal odour. When thrown into a glass 

 containing a concentrated solution of chloride of lime, it soon gives 

 rise to disengagement of bubbles of gas which continue for a some- 

 what long time. In contact with hydrochloric acid it only pro- 

 duces a slight effervescence ; moistened with nitric acid and dned m 

 a porcelain capsule, it assumes a fine red colour. Imally, tnis 

 guano only rarely contains silicious pebbles, and it contains only i 

 to 1-5 per cent of sand ; the maximum is 2-5 to 3 per cent. 



In this same report Girardin gives the analyses of thirteen samples 

 taken by himself on board ship on their arrival m Havre, ihis 

 document is so interesting that it will be useful to reproduce it here 

 The guanos delivered, afterwards were less rich m nitrogen ana 

 more rich in phosphoric acid than those which gave the old 

 analyses. That is not surprising, and each new sample yields 

 different results ; for on the one hand the workmen entrusted with 

 collecting it are not careful enough, on the other hand the deposits 

 are continually altering under the influence of moisture, however 

 small the rainfall in these countries. But the chemical transforma- 

 tion of the guano is not the same in all the parts of a deposit. 



