292 Observations on South American and African Guano. 



its high price as a manure, there is great temptation to adul- 

 terate it, or impose a spurious compost in imitation of it ; and 

 which, indeed, is said to be practised already to a considerable 

 extent, any precise information respecting the genuine article 

 can hardly fail to be useful. With the hope of contributing 

 something of this kind, I have examined both the American 

 and African guano, comparing them together ; and I shall now 

 briefly state the results, premising a slight notice of their ap- 

 pearance. 



Both, when moist or damp, as when imported, and off'ered 

 for sale, are of a pretty dark reddish brown colour, very like 

 that of dark moist snuff. In drying, both become of a lighter 

 hue, and the African kind, on exposure to the air, soon ex- 

 hibits a white efflorescence. Both when moist exhale a strong 

 ammoniacal odour (the African the strongest), mixed with a 

 different and peculiar smell, somewhat offensive, which, with 

 the ammoniacal, they in a great measure lose in drying. 



Under the microscope, using a high power, both appear to 

 consist chiefly of very minute granules, many of them smaller 

 than the blood corpuscles, and of slender prismatic crystals of 

 oxalate of ammonia, in which the African kind is most abun- 

 dant. 



Subjected to chemical analysis, the two kinds (No. 1 the 

 American, No. 2 the African) have appeared to consist of — 



No. 1. No. 2. 



41.2 40.2 Matter soluble in water, destructible by fire or volatile, 

 such as oxalate of ammonia, diphosphate and mu- 

 riate of ammonia, and animal matter. 

 . 29.0 28.2 Matter not destroyed by fire, nor soluble in water, or 

 very slightly so, chiefly phosphate of lime and mag- 

 nesia, with a little sulphate of lime and a very little 

 siliceous sand. 

 2.8 6.4 Matter not destroyed by fire, but soluble in water, 



chiefly common salt, with a little sulphate and 

 sesquicarbonate of potash. 



19.0 ... Matter destructible by fire, little soluble in water, 



chiefly lithate of ammonia. 

 8.0 26.2 Matter expelled in drying on a steam bath, chiefly water 

 and sesquicarbonate of ammonia, 



100.0 100.0 



