"How long will it take to complete the operation?" Goil asked.
"With a cloud this size, about a week. It's best to get on it right away. The tougher metals come out sooner than the softer and lighter metals with lower vaporizing points. Recovery has to be made while the metals are in the vapor state or the gravitors won't work efficiently."
"Exactly how does it work?" asked Goil.
"Well, I guess you might remotely compare it to fractional distillation," I said. "Only we gather metals instead of fluids. The reason for vaporizing the solids is to make the ships accessible to the metals. It spreads the matter out thin. The gravitors work very well in the hot vapor. Behind each ship is towed a gravitor. Each gravitor is set to attract a particular metal, somewhat the way a magnet attracts iron, again loosely comparing. A magnet, as you know, attracts by magnetic force. The gravitors are adjusted to attract a metal by selecting its gravitic attraction. As the gravitor ships pass through the vapor, the gravitors behind them attract the metal they are set for. When load size has been reached, they are taken to the cache near the station."
We watched the operation for three more hours. Goil wanted to see the first of the gravitor tugs emerge with its load. Finally a ship emerged from the cloud mass and headed for the station.
"What is it carrying?" Goil asked, looking at the tremendous mass of incandescent material being towed a mile behind the tug.
"Tungsten," I said. "Would you like to see our cache?"
I steered the little observation ship past the station. When we arrived at the cache area I eased the speed of the ship until it was barely moving around among tremendous masses of various metals. Goil recognized small spheroids of gold and silver. I pointed out other metals, some in greater quantities than others, all floating in space, with thick cables connecting them. I saw Goil looking at the cables curiously.
"Keeps them from drifting apart," I said.