The story opens with a discussion between Barton Swift and an old friend, Alec Peterson.

Swift to finance an expedition to locate a hidden opal mine, but Mr.

In the middle of the conversation, Tom is flying one of his airships, but gets tangled up in power lines.

Tom hopes to sell his invention to the United States government, for use in protecting the Panama Canal, which was still under active construction at the time of the story.

Measuring 100 feet in length, it has a 30-inch caliber, and Tom estimates he can launch a 2 ton projectile 30 miles.