readily used for such purpose. Tell me, what holds you to the Earth,
and makes a stone fall to the ground?"

"Attraction of gravitation," said Rob, promptly.

"Exactly. That is one force I refer to," said the Demon. "The force
of repulsion, which is little known, but just as powerful, is another
that mankind may direct. Then there are the Polar electric forces,
attracting objects toward the north or south poles. You have guessed
something of this by the use of the compass, or electric needle.
Opposed to these is centrifugal electric force, drawing objects from
east to west, or in the opposite direction. This force is created by
the whirl of the earth upon its axis, and is easily utilized, although
your scientific men have as yet paid little attention to it.

"These forces, operating in all directions, absolute and immutable,
are at the disposal of mankind. They will carry you through the
atmosphere wherever and whenever you choose. That is, if you know
how to control them. Now, here is a machine I have myself perfected."

The Demon drew from his pocket something that resembled an open-faced
watch, having a narrow, flexible band attached to it.

"When you wish to travel," said he, "attach this little machine to
your left wrist by means of the band. It is very light and will not
be in your way. On this dial are points marked 'up' and 'down' as well
as a perfect compass. When you desire to rise into the air set the
indicator to the word 'up,' using a finger of your right hand to turn
it. When you have risen as high as you wish, set the indicator to the
point of the compass you want to follow and you will be carried by the