158 Remarks on Priestley’s. Analysis 
water, must fall to the ground; and my own experi- 
ments confirm, as far as analogy goes (what indeed 
hardly admitted of a doubt), that water does not en- 
ter into the constitution of any gas. 
The calx, therefore, which was produced by heat- 
ing iron in oxygenous gas, is a combination of oxy- 
gen and iron; and being one and the same thing 
with finery cinder, this also must be composed of 
oxygen and iron. 
«¢ However,” continues the Doctor, “ neither this 
finery cinder, nor any other calx of iron, can be 
revived unless it be heated in inflammable air, which 
it eagerly imbibes, or in contact with some other 
substance, which has been supposed to contain phlo- 
giston.”——This proves nothing, but that oxygen has 
a greater affinity to iron than to caloric, and that, 
therefore, it cannot be expelled by mere heat. But 
when a substance is present, to which the oxygen 
has a greater attraction than to iron, it will, of 
course, leave this and combine with the other. 
Does the iron, in this process, combine with phlo- 
giston? Let us see what happens when finery cin- 
der is heated in inflammable air. Dr. Priestley, in 
his 3d vol. of Experiments, p. 487, ‘relates the fol- 
lowing beautiful experiment. He put finery cin- 
der into a glass vessel, containing inflammable air 
confined by mercury; and both the vessel and mer- 
cury had previously been made as dry as possible. 
“I had no sooner” says he, “« begun to heat the slag in 
: 
! 
