"You have done well. I'll let you bring the trucks and heavy equipment
while I go ahead with the instruments. Take the road out toward Upper
Marlboro. If I don't meet you before, stop there for orders."

"Very well, Doctor."

"Come on, Carnes, let's go."

* * * * *

He raced down the stairs with the detective at his heels. He went
along the line of touring cars and spoke briefly to the drivers. He
climbed into the car which Carnes had brought. As it started the other
cars fell in behind it. At a speed of forty miles an hour, with a
detachment of motorcycle police leading the van, the cavalcade rolled
out through the deserted streets of Washington. Once clear of the
city, the speed was increased.

"Did you persuade the President to leave?" asked the doctor.

"There wasn't a chance. The papers panned him so much for following my
advice at Charleston that he has turned stubborn. He says that if all
the forces of the government can't protect him against one man, he is
willing to die."

"We've got to save him," said Dr. Bird grimly. "Hello, there's the
Chesapeake ahead."

The doctor studied the country.

"We are about opposite the place where we left that sub last night. I
fancy that Saranoff will operate from there, for it didn't move during
the last half hour we watched it. We'll go back inland a mile or two
and spread out. I have no idea how far his radiations will affect the
electroscopes, but we'll try four hundred-yard intervals to start.
That will enable us to cover a line twelve miles long."

He picked up a megaphone and spoke to the line of cars behind him.

"Take up four hundred yard intervals when we spread out," he said.
"Every man keep his headphone on and listen for orders. Follow my car
until it stops, then turn north and south and drop your men at
intervals."

He reentered the car and led the way back for two miles. He halted his
car at a crossroad. The cars following him turned and went to the
north and south. Besides Carnes and the doctor, the car held two men
from the Bureau. As they climbed out, Carnes saw that one of them
carried a portable radio sending set, while the other bore an
electroscope and a rubber rod. The radio operator set up his device,
while the other man rubbed his coat sleeve briskly with the hard
rubber and then touched the ball of the electroscope with it. The two
bits of gold-leaf spread out.

"While we're waiting, I'll explain something