Free Fallen Star by James Blish Page B

nevertheless, I was glad not to be with her.
    We flew all day and well into the evening. Night fell before we crossed the Sixtieth Parallel, but the ground cover was already
     sparse by the time the last light failed. This far north, only a few dwarf spruces struggled up against the cold, and at the
     Sixtieth we would cross the “tree-line”, that line which not only divides the trees from the snows, but in Canada traditionally
     divides the Indians from the Eskimos.
    The cabin door opened and the Commodore came out, I suppose because there was nothing more to be seen that day, and came down
     the aisle. He settled in the seat across from mine, looking pleased with himself.
    “Who’s minding the store?” I asked him.
    “Hanchett. We’re on autopilot, and he’s watching the instruments. If anything goes wrong he’ll call me; he knows enough to
     detect any trouble.” He reached into one of his jacket pockets. “Tell me, Julian, have you ever seen anything like this before?”
    “This” proved to be a piece of crudely shaped glass, darkgreen in colour, about as big as my hand. It was roughly crescent-shaped; on one wing of the crescent, on the outside curve,
     there was a sort of pool or apron of the same glass, circular when looked down upon.
    “No,” I said, hefting it. It weighed perhaps a quarter of a pound. “Doesn’t look much like bottle-glass. What is it?”
    “It’s Darwin glass—australite.”
    “Sorry, I’m no geologist. What is it supposed to tell me?”
    “Darwin glass,” the Commodore explained, “is meteoric. It’s one member of a whole family of such glasses, called tektites.
     They’ve fallen all over the Earth, probably long ago —paleolithic man used them as weapon points. See that puddle?” He pointed
     to the apron on the back of the crescent. “That’s where the surface fused in flight, and the glass flowed back to that point
     because of the wind-pressure.”
    Now I was beginning to get his drift. He was back on his favourite hobby-horse, the asteroidal protoplanet. “Do you think
     they’re parts of Planet Four-and-a-half?”
    “They couldn’t be anything else. Whether or not they were in this glass form when they were actually part of the planet is
     a tough question. It’s possible that glass pools formed on the surface while the planet was still hot, if you assume a world
     about the size of the Earth, as you pretty well have to. You need a planet with a nickel-iron core, surrounded by a mantle
     of triolite and olivine, with a top coat of silicates—just like us. Otherwise you can’t account for the distribution of meteor-types
     in any systematic way.”
    “A planet with a glass skin!” I said. “That would be a novelty.”
    “I didn’t say that,” the Commodore objected. “I said silicates—which could mean sand, granite and so on. It’s my notion that
     the tektites were originally parts of comets that passed through the outer layers of the sun’s atmosphere, and got converted
     into glass there. I don’t see any other way to account for the low gas pressure they show.”
    “Then that would indicate that they
weren’t
once part of the asteroidal planet, wouldn’t it? Comets are supposed to be formed independently.”
    “Unproven,” he said. “I think it’s a lot likelier that meteors are just the debris of comets, and that they all came out of
     the asteroid belt originally.”
    “Then what happened there originally?”
    “Probably a collision,” Farnsworth said broodingly. “If there were originally two planets in that area, Jupiter would have
     been shifting their orbits constantly. After all, the accident had four thousand million years to happen in. The very first
     tektites fell on the Earth no more than fifty million years ago—and the same seems to hold true of all meteorites, of every
     kind. You never find them in strata older than that. So the accident was recent.”
    “You make a good case,” I told him sincerely.
    “I