The story begins with startling intimacy:
I don't know why; most men shift their quid after they hitch up their trousers.
The Transient Lake, which gives the tale its title, is a body of water that disappears from time to time, revealing a vast store of gold. Frank's interested, but purely from a scientific point of view, of course. He doesn't need gold. His inventions pay for themselves, somehow. Even though no one else has subs or planes.
At the end there's the usual dose of Good-Humored Ribbing. Captain Nicodemus. What a fine 19tth century name. Captain Nicodemus Beere.