h on the bird," was Anton's sympathetic comment.

"Not especially! As soon as a bird begins to show collapse, it is
taken back to the open air and is as frisky and lively as ever in five
minutes. But its value as a warning signal is enormous, for it tells
rescue parties or investigating parties when to put on gas masks or
breathing apparatus containing oxygen. In a well-ventilated mine,
however, where high explosive is used and handled by experienced men,
there's not likely to be much danger from white damp.

"Stink damp is rare but can sometimes be dangerous. Generally, a
fellow is warned away, because of the smell--which is just like rotten
eggs. The worst part of stink damp is that it smells the worst when
there's only a little of it. When there's so much of it around as to
be deadly, it doesn't smell any worse. You get small quantities of it,
sometimes, in blasting, but generally hydrogen sulphide or stink damp
is found after a mine fire or an explosion. Rescue parties generally
carry a cage of mice as well as one of canaries."

"With the same idea?" queried Anton.

"Exactly. As little as a tenth of one per cent. of stink damp makes a
mouse sprawl on his belly, his legs don't seem strong enough to hold
him up; while, in the same air, a canary doesn't suffer a bit.

"The only real danger in stink damp is when there's water in the mine,
for example when, after a fire, a lot of water has been pumped down
into the workings to put the fire out. Water absorbs stink damp very
easily and gives it up equally easily when stirred. So, if a member of
a rescue party puts his foot in a puddle of water where there has been
stink damp around, so much of the gas may suddenly come up in his face
as to topple him over.

"But you can see, Anton, that most of the gas troubles in a mine come
from the blasting. That's why, nowadays, the miners who get out the
coal seldom or never fire the shots. Experienced men, trained
especially for that work, are used. After a miner has undercut the
coal, the shot-firer comes. He tests for gas before he begins work,
bores a deep hole in the coal with a drill, tests for gas again in
case he should have tapped a leak in the seam, cleans out the hole,
sends the miner for the box of explosive--which is kept thirty or
forty yards away from the face where the coal is being cut--and
prepares the charge with a detonater which he carries in a box over
his shoulder. The miner never touches either the explo