os, 
the Formation of Guano. 227 
As we know that the sun’s rays have, in many instances, 
a remarkable effect as a chemical agent, it occurred to me as 
probable, that the oxalic acid found in guano might be pro- 
duced from the lithic acid of the urine of birds, in conse- 
quence of the agency of the light of the sun, aided by an 
accompanying high temperature, such as must prevail in a 
tropical climate. 
To submit this conjecture to the test of experiment, a por- 
tion of the solid urine of the white-headed sea-eagle, slightly 
moistened with water, was put into a glass tube, with a cork, 
having a small notch in it to allow of the entrance of air,— 
and suspended against a southern wall, where it was exposed 
to sunshine or strong light the greater part of the day. The 
experiment was commenced on the 20th of last March, and 
continued till the 3lst of May. During this period of 70 days, 
the weather, a great part of the time, was unusually fine 
and dry; only 5 inches of rain fell from the 20th of March 
to the 30th of April, and only .13 of an inch from the 1st to 
the 31st of May; and more than half the time, viz., about 
47 days, there was bright sunshine. The range of tempera- 
ture at the same time was great, even in the shade, extend- 
ing from below the freezing point, which it often was during 
the clear nights, to 60° and 65° by day. 
The urine of the sea-eagle, the subject of the experiment, 
previously examined, was found to consist chiefly of lithate 
of ammonia, with a little animal matter, and to be entirely 
destitute of oxalic acid. After exposure, it was found, on 
examination, to contain a small proportion only of lithic acid, 
and a large proportion of oxalic acid in combination with 
ammonia. Its resemblance now to guano was remarkable. 
It had a strong ammoniacal odour, mixed with the peculiar 
odour of guano. Under the microscope, it was found to 
abound in prismatic crystals, such as occur in guano, and 
which, as they were soluble in water, and yielded, with mu- 
riate of lime, a copious precipitate of oxalate of lime, were 
evidently crystals of oxalate of ammonia; and, in accordance 
with this composition, a portion of them put by have remained 
unaltered in their form, after exposure to the air now more 
than six months. With the odour of the guano, the lower 
