228 Dr Davy on some Experiments tending to illustrate 
portion of the mass had acquired a brown colour, not unlike 
that of guano, and, like its colouring matter, soluble in 
water; whilst its upper surface was almost colourless, being 
formed chiefly of oxalate of ammonia, nearly pure, in needle 
crystals, visible to the naked eye, collected in little stella- 
form groups, presenting, even in this circumstance, another 
resemblance to guano, in which often light-coloured masses 
are met with, composed principally of the same salt. 
The next experiments made were of a comparative kind, 
with a view to endeavour to determine whether the action 
of light is really essential to the conversion; whether the 
presence of atmospheric air is essential ; and whether lithic 
acid, uncombined with ammonia in its pure state, is capable, 
under the influence of light, of being changed into the oxalate 
of ammonia. 
Accordingly, a portion of the same urine of the sea-eagle, 
moistened, was exposed to light as before; another portion 
was put by in a dark place; a third was confined over mer- 
cury in a glass tube, in which was a measured quantity of 
atmospheric air, and so placed as to be well exposed to light 
and sunshine ; and, lastly, a portion of lithic acid, moistened, 
was similarly exposed, but not confined over mercury. 
These experiments were begun on the 7th of last June, 
and they were continued until the 15th of October. During 
this time, comprising 100 days, there was a much larger 
proportion of gloomy weather than during the period of the 
first experiment ;—this is pretty correctly indicated by the 
number of days in which rain fell, viz. 80, and the total 
quantity of rain, viz. 26.05 inches, as measured by the rain- 
gauge; and at the same time the atmospheric temperature 
was more uniform, with few exceptions, cool by day, and not 
cold at night. 
The result of the experiment No. 1, namely, that in which 
the moistened urine of the sea-eagle was exposed to light, 
atmospheric air not being excluded, was similar to that of 
the preceding, but less strongly marked. 
The result of the 2d experiment, namely, of that in which 
the urine, moistened, had been kept excluded from light, was, 
too, generally similar: the urine was found to have an am- 
