"The tubes, Greg. It just ain't no use. We can't operate the radio less'n we got tubes, and ours is gone. I guess I'm just wasting my time."
Greg said, "Isn't there a type of radio that works without tubes? Operates on a crystal, or something?"
Sparks said, "Yeah. But it ain't got no power. We got to get a message plumb off the satellite, out into space where it can be picked up by a Space Patrol cruiser. Or the Saturn lightship."
"And that's impossible? Suppose you had glass?"
"Can you make it?" scoffed Sparks.
"Maybe," said Greg. "Glass was accidentally discovered in the first place, you know, by Phoenician sailors who built a fire on a sandy beach wherein was imbedded raw chunks of natron. We might be able to do the same."
Sparks shook his head glumly. "O.Q. So that gives us glass. We still got to blow it, and figger out some way of sucking the air out, and winding filaments. Oh, understand, I ain't saying we can't do it, Greg. But it'll take years."
Greg nodded soberly.
"Well, we'll overlook no bets. Sparks—tell you what to do. You go ahead and build one of those simple 'crystal' sets, just in the event that someday a scout ship or exploration plane should come within our range. Andrews is an important man, you know. Earth won't dismiss him casually as 'Lost in Space.' We'll also, as soon as the Sun comes back, clear a wide swath in the plain below us and construct a huge SOS sign of wood and underbrush that will be visible by day and can be set afire by night.
"Then, if we should ever hear the signal of a scout ship, we'll hope they see our marker."