294 Observations on South American and African Gttano. 



ing on grass, from the pigeon, the common fowl, the gull, the 

 pelican, and the white-headed sea eagle, — the three latter in 

 the garden of the Zoological Society of London, where they 

 are fed chiefly on fish, and the gulls entirely so, as I am in- 

 formed by my friend Mr Gulliver, to whose kindness I am in- 

 debted for the specimens. 



The urine from each of these birds, in its purest state, or 

 least mixed, was very similar ; of an opaque white, sometimes 

 with a stain of brown. Under the microscope, it appeared to 

 be composed chiefly of granular matter, each particle seldom 

 exceeding in size a blood corpuscle, viz., that of man, and com- 

 monly less. In the instance of the urine of the sea-eagle, de- 

 licate tabular crystals were mixed with the molecules. Sub- 

 mitted to chemical examination, each kind was found to con- 

 sist chiefly of lithate of ammonia, with a little phosphate of 

 lime and magnesia. In that of the goose, a trace of urea 

 was detected, with a little carbonate of lime and magnesia ; 

 and in that of the sea-eagle, a small portion of oxalate of 

 lime, constituting the tabular crystals seen under the micro- 

 scope. In each instance, search was made, but in vain, for 

 oxalate of ammonia, — not a trace of it could be detected ; and 

 thus tending to confirm the conclusion of M. Liebig, that this 

 salt results in guano, from the decomposition of lithic acid, 

 and the new arrangement of its elements, aided, I would add, 

 by the absorption of oxygen from the atmosphere. 



That atmospheric oxygen is concerned in this change, I am 

 induced to infer from some experiments which I have made. 

 I shall briefly notice two. Lithate of ammonia (the urine of 

 the sea-eagle) in a moist state, was subjected in a close vessel 

 to the temperature of boiling water, for about twenty-four 

 hours, when it was tried for oxalate of ammonia ; but not a 

 trace of this salt could be detected. It was next exposed to 

 the same temperature, mixed with black oxide of manganese^ 

 and for about the same time. Now, the presence of oxalate 

 of ammonia was clearly indicated, for the mixture, after 

 digestion, with a little water and filtered, yielded a solution, 

 which, after having been made slightly acid, was rendered tur- 

 bid by muriate of lime, and the precipitate had the properties 

 of oxalate of lime. I may mention further, that the aqueous 



