"Nothing for the Althea. But plenty to prevent any more disasters like it." There was a hard ring to his voice. "Come on." He stepped off the transparent slab onto the stone floor of the island.
"Where to?" asked Nona, following.
"We're going to locate that orange oval we saw from the Althea. That's the secret of all this. The pool of liquid fire here is unimportant, secondary."
They were at one edge of the floating island. The other side was hidden from them by the solid wall that stretched across its full diameter.
"We'll scout beyond there," Grant pointed out. "I'll miss my guess if what we're looking for is not on the other side."
As they started for the wall, they saw the Althea brought slowly down to the rock, another captive to swell the motionless fleet. It did not take them long to reach the barrier. Some fifty feet high it was, of smooth polished Ganymedan stone, and no door or opening in its straight unbroken surface.
"How shall we get through?" Nona asked.
Grant surveyed it thoughtfully.
"There must be a hidden spring somewhere," he said.
He walked carelessly along the wall, tapping it idly here and there. His quick probing fingers were searching.