relating to Air and Water, 
much. This laft circumftance, however, fome of my experi- 
ments may ferve to explain. Whenever I had no more water 
than was fufficient for the production of the air, there was 
never any fenfible quantity of uncombined fixed air mixed with 
the inflammable air from charcoal. This was particularly the 
cafe when I produced the air by means of a burning lens in an 
exhaufted receiver, and aifo in an earthen retort with the appli- 
cation of an intenfe heat. I therefore prefume, that when the 
fleam tranfmitted through the hot tube containing the charcoal 
was very copious, the fixed air in the produce was greater than 
it would otherwife have been. The extremes that I have ob» 
ferved in the proportion of the fixed to the inflammable air have 
been from one-twelfth to one-fifth of the whole. As I gene- 
rally produced this air, the latter was the ufual proportion ; and 
this was exclufive of the fixed air that was intimately combined 
with the inflammable air, and which could not be feparated 
from it except by decompofition with dephlogifticated air ; and 
this combined fixed air I fometimes found to be one-third of the 
whole mafs, though at other times not quite fo much. 
To afcertain this, I mixed one meafure of this inflammable 
air from charcoal (after the uncombined fixed air had been fepa- 
rated from it by lime-water) with one meafure of dephlogifti* 
cated air, and then fired them by the eledlric fpark. After this^ 
I always found that the air which remained made lime-water 
very turbid, and the proportion in which it was now dimi- 
nifhed, by walking in lime-water, fhewed the quantity of 
fixed air that had been combined with the inflammable. That' 
the fixed air is not generated in this procefs, is evident from, 
there being no fixed air found after theexplofion of dephlogifU- 
eated air and inflammable air from iron. 
Notwith^ 
