5^4 H. Davyds Experments on the 
purity of the oxygene gas with which the globe was filled had 
not been determined before the experiment, it was impossible 
to ascertain with precision, that no elastic matter had been 
emitted during the process. To determine this point, I made a 
third experiment. A thin diamond weighing .93 of a grain 
was introduced into the platinum capsule, which was placed 
in a globe filled with water and inverted in water, some oxy- 
gene gas, the last portion from the decomposition of hyper- 
oxy muriate of potassa, was thrown into the globe, so as to 
displace the water below the level of the capsule. The focus 
of the great lens was thrown upon the capsule, which with the 
diamond was instantly rendered dry by it, and the diamond 
soon entered into combustion and burnt as usual. After the 
process was finished, the carbonic acid was absorbed by lime 
water, and the remaining gas, which equalled about one-third 
of the quantity of oxygene originally used, was compared 
analytically in several experiments with a portion of the same 
oxygene as that introduced into the globe, two measures of 
nitrous gas being added to a measure of each of the gases ; 
the diminution was less by from to parts in the cases 
in which the gas that had been exposed to the action of the 
diamond was used ; but this minute difference is what might 
have been expected, and which indeed could not fail to exist, 
when it is considered that, during the absorption of carbonic 
acid gas by water and lime water, a small quantity of common 
air is always expelled from the water. 
In this last experiment a small fragment of diamond re- 
mained unconsumed, which was similar in appearance to that 
mentioned in the second experiment, and its colour, which was 
originally yellow, was rendered rather darker. In no one of 
