relating to JJir and Wafer, 299 
Confidering how little this inflammable air weighs, viz. the 
whole 1054 ounce meafures not more than 63 grains, and the 
difficulty of afcertainmg the lofs of water to fo fmall a quan- 
tity as this, it is not poffible to determine, from a procefs of 
this kind, how much water enters into the compofition of the 
inflammable air of metals. It would be more ealy to deter- 
mine this circumftance with refpeft to the inflammable air of 
charcoal, efpecially by means of the experiment made with a 
burning lens in vacuo. In this method two grains of charcoal 
gave at a medium thirteen ounce mealures of inflammable air, 
which, in the proportion of 30 ounce meafures to 8 grains, 
will weigh 3.3 grains; fo that water in the compofition of this 
kind of inflammable air is in the proportion of 1 . 3 to 2 , though 
•there will be forne difficulty with refpefl to the fixed air inti- 
mately combined with this kind of inflammable air. 
Since iron gains the fame addition of -weight by melting in 
dephlogijlicated air , and alfo by the addition of water when 
red-hot, and becomes, as I have already obferved, in all re- 
fpedsthe fame fubftance, it is evident, that this .air or water , as 
exifting in the iron, is the very fame thing ; and this can 
hardly be explained but upon the fuppofition that water confifls 
of two kinds of air; viz. inflammable and dephlogiflicated. 
1 ffiall endeavour to explain thefe proceffes in the following 
manner. 
When iron is melted in dephlogiflicated air, we may fuppofe 
that, though part of its phlogifton efcapes, to enter into the 
compofition of the final! quantity of fixed air which is then 
procured, yet enough remains to form wafer with the addition 
of dephlogiflicated air which it has imbibed, fo that this calx 
of iron confifts of the intimate union of the pure earth of iron 
and of water ; and therefore when the fame calx, thus fatu* 
Q q a rated 
