360 Abbe fontan a ? s Experiments and 
that the inflammable air is the more difficult to be de- 
compofed, by being fhaken in water, as the number of 
the fparks it fhews when burning is greater; and ac- 
cording to this number of fparks, the inflammable air 
makes greater or weaker explofions when mixed with 
the dephlogifticated air; fo that it feems proved by expe- 
ments, that the phlogiftic principle is more fixed and in 
greater quantity combined with the inflammable air of 
metals, than with that of vegetable or animal fubftances. 
I do not mean to deny the poflibility of finding other fpe- 
cies of inflammable air extracted from other fubftances 
befides metals which may explode like that extracted 
from metals ; but I only fay, that in thofe cafes the in- 
flammable air will alfo fparkle more, and will be found 
lefs eafy to be decompofed by water. There are othei* 
fubftances that give the inflammable air in great quan- 
tity, and which cannot be confidered as animal or vege- 
table fubftances, but come rather near the nature of me- 
tals; as, for inftance, the fpathofe iron, from which I ex- 
tract a good deal of inflammable air by the adtion of fire 
only, applied to a mattrafs. But the metal in this fub- 
ftance is not in its pure ftate, and it may be confidered 
rather as a calx of iron than true iron. Accordingly, 
this air can hardly fparkle at all ; it explodes more like 
a the 
