t 3?* J 
XX 111, Experiments on Air, 
By Henry Cavendifh, EJq. r\R.S. and A.S* 
Read June 2, 1785. 
I N a Paper, printed in the lad: volume of the Philofophical 
Transitions, in which I gave my reafons for thinking that 
the diminution produced in atmofpheric air by phlogiflication 
is not owing to the generation of fixed air, I faid it feemed mod 
likely, that the phlogiflication of air by the electric fpark was 
owing to the burning of fome inflammable matter in the appa- 
ratus ; and that the fixed air, fuppofed to be produced in that 
procefs, was only feparated from that inflammable matter by 
the burning. At that time, having made no experiments on 
the fubjedf myfelf, I was obliged to form my opinion from 
thofe already publifhed ; but I now find, that though I was 
right in fuppofing the phlogiftication of the air does not pro- 
ceed from phlogiflon communicated to it by the eledlric fpark, 
and that no part of the air is converted into fixed air ; yet that 
the real caufe of the diminution is Very different from what I 
fufpedted, and depends upon the converfion of phlogiflicated 
air into nitrous acid. 
The apparatus ufed in making the experiments was as follows. 
The air through which the fpark was intended to be pafled, was 
confined in a glafs tube M, bent to an angle, as in fig. 1 . (tab, 
XV.) which, after being filled with quickfilver, was inverted 
into two glalfes of the fame fluid, as in the figure. The air to 
be 
