moment he looked puzzled, then he smiled.

"I think I've got it!" he said. "They're clever enough to try to
fool anyone who got on to their signalling. They would know what
everyone would think -- that they would be sending their messages
to the East coast, because that is nearest to Germany. That's why
they put their first station here. I'll bet they send the flashes
zig-zagging all around, but that we'll find they all get east
gradually. Now we'll circle around this one until we find out in
what direction it is flashing, then we'll know what line we must
follow. After that all we've got to do is to follow the line to
some high hill or building, and we'll pick up the next station."

Their eyes were more accustomed to the work now, and they wasted
very little time. This time, just as Harry had guessed, the
flashes were being sent due east, and judging from the first case
that the next station would be less than ten miles away, he
decided to ride straight on for about that distance. He had a
road map, and found that they could follow a straight line, except
for one break. They did not go near the hilltop at all.

"I'd like to know what they're doing there," said Dick.

"So would I, but it's open country, and they're probably keeping a
close lookout. They're really safer doing that in the open than
on the roof of a house, out here in the country."

"Because they can hide the heliograph? It's portable, isn't it?"

"Yes. They could stow it away in a minute, if they were alarmed.