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a great extent in South America, and which is the 
manure that fertilizes the sterile plains of Peru, is 
a production of this kind. It exists abundantly, 
as we are informed by M. Humboldt, on the small 
islands in the South Sea, at Chinche, Ilo, Iza, and 
Arica. Fifty vessels are laden with it annually at 
Chinche, each of which carries from 1500 to 2000 
cubical feet. It is used as a manure only in very 
small quantities ; and particularly for crops of 
maize. I made some experiments on specimens of 
guano sent from South America to the Board of 
Agriculture in 1805. It appeared as a tine brown 
powder ; it blackened by heat, and gave off strong 
ammoniacal fumes ; treated with nitric acid it 
afforded uric acid. In 1806 MM. Fourcroy and 
Vauquelin published an elaborate analysis of guano. 
They state that it contains a fourth part of its 
weight of uric acid, partly saturated with ammo- 
nia, and partly with potassa ; some phosphoric acid 
combined with the same bases, and likewise with 
lime. Small quantities of sulphate and muriate 
of potassa, a little fatty matter, and some quart- 
zose sand. 
It is easy to explain its fertilizing properties : 
from its composition it might be supposed to be a 
very powerful manure. It requires water for the 
solution of its soluble matter to enable it to pro- 
duce its full beneficial effect on crops. 
The dung of sea birds has, I believe, never been 
used as a manure in this country ; but it is probable, 
that even the soil of the small islands on our coast 
much frequented by them, would fertilize. Some 
dung of sea birds brought from a rock on the coast 
