Oil (he Food of Plantit. 
543 
saturated with ammonia and partly with potash, phosphates of 
these bases and of Hme, a little sulphate and chloride, and some 
siliceous sand. 
The guano is described by Sir H. Davy in his admirable 
lectures on agricultural chemistry, but seems to have been for- 
gotten until the publication of Liebig's volume, since which a 
small quantity has been imported. It is a substance deserving 
the attention of agriculturists, as it is one of those manures best 
able to bear the expense of transport, containing much valuable 
matter in a small space. 
An excellent paper on guano, by Professor Johnston, is to be 
found in the last published Number of the Journal of the Society, 
to which the reader is referred. This paper contains an account 
of some experiments made with the substance as a manure, which 
were decidedly successful, a set of new analyses, and some re- 
marks on its use, which deserve attention. Unfortunately, how- 
ever, for the English farmer, it seems not improbable, from the 
statements referred to, that the supply itself is likely after a time 
to fail, as the increasing commerce along the coast frequented by 
the sea-birds has already in part driven the latter from their 
accustomed haunts, and thus interfered with the production of 
the substance. Guano is a substance exceedingly variable in 
composition, and, consequently, in value — a point which must be 
kept in mind. The following analysis, on the authority of Volkel, 
made on a specimen of a quantity brought from Valparaiso * will 
serve as an illustration of its general nature. 
100 parts contained — 
Urate of ammonia . . . . 9*0 
Oxalate of ammonia .... 10'6 
Oxalate of lime . . .. . 7'0 
Phosphate of ammonia . . . .6*0 
Phosphate of magnesia and ammonia . . 2*6 
Sulphate of potash . . . . 5'5 
Sulphate of soda . . . . . 3 • 8 
Sal-ammoniac , . . . . 4'2 
Phosphate of lime . . . . 14'3 
Clay and sand . . . . . 4 ' 7 
Various organic matters, a little soluble salt 1 32-3 
of iron, and water . . . . ) 
100-0 
The occurrence of so much oxalic acid is a curious subject of 
speculation ; it must be a result of the chemical changes which 
the guano is constantly undergoing, and which form the principal 
^ Annalen der Chemie imd Pharmacia, pp. 39, 289. 
VOL. IV. 2 N 
