230 Dr Davy on some Experiments tending to illustrate 
notable portion of this salt, when exposed to the same tempe- 
rature, mixed with some black oxide of manganese; and, it 
may be worthy of remark, that, in this instance too, a brown 
soluble matter appeared to be developed. 
From the negative results of the experiments in which 
lithic acid, moistened, was exposed to light, may it not be 
inferred that the presence of some foreign matter, acting as 
a leaven, is necessary to excite, and, with oxygen, to effect, 
the conversion of the lithate of ammonia into the oxalate ? 
In corroboration, I may remark, that on the addition of am- 
monia to the lithic acid, converting it into lithate of ammo- 
nia, the same negative results were obtained, after exposure 
to light, not excluding the access of atmospheric air during 
a period of 74 days, namely, from the 15th of October to the 
29th of December. 
To return to guano.—Comparing the Peruvian with the 
African, I have always found, in accordance witb the preced- 
ing remark relative to the influence of the sun’s rays, a 
larger proportion of lithate of ammonia in the former than 
in the latter :—in the latter, indeed, I have never found more 
than a trace of this substance, and in many specimens I have 
not been able to detect even a trace of it; instead, there has 
been a large proportion of the oxalate. May not this be 
owing to the different states of atmosphere on the two coasts ; 
the one always shrouded by clouds intercepting the direct 
rays of the sun, and enfeebling their action; the other com- 
monly clear, permitting the sun’s rays to act with full 
effect? And may not the short time in which the conversion 
of the lithate of ammonia into the oxalate takes place, as 
shewn in the first experiment detailed, help to explain the 
absence of the lithate even in specimens of guano taken from 
the surface, and of recent production? Such a specimen I 
lately received, brought from the island of Ichaboe, off the 
African coast, described ‘‘ as having been scraped off a rock, 
where it was in a thin layer, much exposed to the sun,” in 
which I could not detect the smallest quantity of lithate of 
ammonia, but abundance of oxalate. The effect of the sun’s 
rays in accelerating the conversion of the lithate into the 
