Enough to make every American shiver, if he only knew!"

"What can we do about it?" Bud asked.

Tom resumed his worried pacing. "I'll have to invent a shock-wave
deflector, Bud. It must be done in a hurry, too. Our enemy may start to
destroy American cities as well as vital defense plants!"

Immediately Tom put through an urgent call to an eminent scientist in
Washington who was a member of the National Research Council. Quickly he
outlined a plan.

"Tom, I'll talk to the president's special science adviser at once," the
man promised. "I'll try to set up a meeting for ten o'clock tomorrow
morning at Enterprises."

Feeling relieved, Tom left the plant with Bud. The two boys drove off to
attend church with Mrs. Swift and Sandy. Then, after the Sunday midday
meal, Tom returned to his laboratory to work on ideas for a shock-wave
deflector.

Bud and Sandy, meanwhile, drove to the Shopton Yacht Club to inspect the
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