"That's one!" cried Jim. "I'm afraid we won't have time to hunt up the other right now. This bug told me that the other Mercurians are due here to-day, and I think we had better form ourselves into a reception committee and go up to the hole to meet them."
He sent the ship at high speed over the city until we hovered over the laboratory. We stopped for a moment, and Jim stepped to the radio telephone.
"Hello, Williams," he said, "how are things going? That's fine. In an hour, you say? Well, speed it up as much as you can; we may call for it soon."
He turned both stern motors to full power, and we shot up like a rocket toward the hole in the protective layer through which the invaders had entered. In ten minutes we were at the altitude of the guard ships and Jim asked if anything had been seen. The report was negative; Jim left them below the layer and sent our flyer up through the hole into space. We reached the outer surface in another ten minutes and we were none too soon. Hardly had we debouched from the hole than ahead of us we saw another Mercurian flyer. It was a lone one, and Jim bent over the captive and held a hastily made sketch before him. The sketch showed three Mercurian flyers, one on the ground, one wrecked and the third one in the air. He touched the drawing of the one in the air and pointed toward our port hole and looked questioningly at the beetle. The insect inspected the flyer in space and nodded.
"Good!" cried Jim. "That's the third of the trio who came ahead as scouts. Get your gun ready, First Mortgage: we're going to pick him off."
Our ship approached the doomed Mercurian. Again I waited until we were within four hundred yards; then I pressed the button which hurled it, a crumpled wreck, onto the outer surface of the heaviside layer.
"Two!" cried Jim as we backed away.
"Here come plenty more," I cried as I swung the searchlight. Jim left his controls, glanced at the screen and whistled softly. Dropping toward us from space were hundreds of the Mercurian ships.
"We got here just in time," he said. "Break out your extra ammunition while I take to the hole. We can't hope to do that bunch alone, so we'll fight a rearguard action."