"Exactly. The set-up was perfect. Our apparatus was, perforce, crude,
but we had all the elements of a refrigerating unit. Ammoniated water,
running in a constant stream, capsules of condensed and concentrated
heat from our needle-guns--a small room which was connected, by
ventilating ducts, with the rest of the underground city.
"The principle of the absorption process depends on the fact that
vapors of low boiling point are readily absorbed in water and can
be separated again by the application of heat. At 60°F, water
will absorb about 760 times its own volume of ammonia vapor, and
this produces evaporation, which, in turn, gives off vapor at a low
temperature, thereby becoming a refrigerator abstracting heat from any
surrounding body. In this case--the rooms above!
"It--" Tim grinned. "It's as simple as that!"
Captain Lane groaned.
"Simple!" he echoed weakly. "The man says 'simple'! I don't understand
a word of it, but--it worked, son! And that's the pay-off."
"No, sir," said Tim promptly.
"What? What's that?"
"The pay-off," persisted Tim, "comes later. When we get back to
civilization. You said something about removing your objections to our
marriage, remember?"
Captain Jonathan growled and stood up. "Confound it, do you think of
everything? Well--all right, then. I'm a man of my word. But when we
get back to civilization may be a long time yet."
"I can wait," grinned Tim. "But I've got a feeling I won't have to wait
long. Maybe I'm psychic all of a sudden. I don't know. But somehow I've
got a hunch that when we get to the cave-mouth, we're going to find a
rescue party waiting for us up there. I just _feel_ that way."
"Humph!" snorted Lane. "You're a dreamer, lad! A blasted, wishful
dreamer!"
But it was a good dream. For the hunch was right.