damage to the _Sunspot_. Tom had arranged with a salvage crew to tow the
disabled ketch back to its slip.

Monday morning, a sleek Air Force jet transport touched down at Swift
Enterprises. Aboard were a select group of top government scientists.
Tom and Bud greeted them as they disembarked on the runway, then drove
them to a conference room in the Enterprises main building.

"I'd say your theory is right, Tom, about the quakes being produced by
artificial shock waves," said Bernt Ahlgren, a tall, hawk-faced man with
a shock of red hair. He was a member of the Defense Department's
Advanced Research Projects Agency. "But how do we stop them?"

"I believe they can be damped out by opposing waves," Tom replied. "This
is assuming that I can design the right sort of equipment to do the
job--and also that we can set up a warning system to alert us of the
enemy shock waves in time." The young inventor sketched out the sort of
shock-wave deflector which he had in mind. The government experts were
very much impressed. In the session that followed, the visiting
scientists contributed many tips and suggestions. Tom noted them down
gratefully.

After a thorough discussion, it was agreed that the Defense Department
would set up detectors at fifty check points around the country. Tom
would choose the exact spots. Detection data from the check points would
be fed to an electronic computer. The computer would establish the
pattern, if any, of incoming enemy shock waves.

Dr. Gregg Miles, a seismologist from the Bureau of Mines, agreed to take
on the job of setting up the check points.