"We'll prob'ly find a portable sender, sir, an' trail the Wabbly. That's about all we can do, sir."

"It looks," said the major-general rather desperately, "as if that is all anybody can do. I'm going on to take command ahead."

The 'copter pilot said politely:

"Sir, if you're going to sow mines for the Wabbly—"

"Of course!"

"That power-beam can explode them, sir, before the Wabbly gets to them. May I suggest, sir, that mine-cases with no metal in them at all would be worth trying?"

"Thank you," said the major-general grimly. "I'll have concrete ones made."

Sergeant Walpole grunted suddenly.

"Look here, sir! The Wabbly stops when it uses that dinkus on top. This guy here says it uses a lotta power—four or five thousan' horsepower."

"More likely ten or twenty," said the 'copter pilot.