last all was in readiness for the gas test.

It was proposed to try it on an experimental scale. Some of the fluid
was to be generated and forced into an aluminum cylinder under the
same pressure it would be used in the air ship. To this cylinder were
attached weights in proportion to the weight of the Flying Mermaid
with its load of human freight, engines and equipment.

"This cylinder is just one one-hundredth the size of the cylinder of
the ship," said the professor. "I am going to fasten to it a hundred
pound weight. If it lifts that our latest contrivance will be a
success."

"You mean if the little cylinder pulls a hundred pounds up the big
ship will take us and the machinery up?" asked Mark.

"Certainly," answered the professor. "If this cylinder lifts a hundred
pounds, one a hundred times as big (as that of the Mermaid is), will
lift a hundred times as much, or ten thousand pounds. That is five
tons, or more than a ton over what I figure to be the weight of our
ship and contents. The latest war balloon can lift one ton with ease,
and if my machine can not do five times as well I shall be
disappointed."

The last adjustments were made, pipes were run from the gas generator
to the cylinder, and the hundred pound weight was attached.

"Everybody look out now," said Mr. Henderson. "I am going to start the
machine and let the gas enter the cylinder. It is a very powerful gas
and may break the cylinder. If it does you must all duck."