Thus the spark of fire that falls is the occasion of an explosion, but the cause of the havoc is the relation between charcoal, niter and saltpeter.
"The Art of Public Speaking"
Dale Carnagey (AKA Dale Carnegie) and J. Berg Esenwein
Probably extract their niter from the dung of their horses and cows.
"The Return"
H. Beam Piper and John J. McGuire