ul example of this kind of motion. In
the great pyramid of Khufu, Rick had read, a channel had been left so
the light of the North Star could shine on the altar of Isis. The
channel was still there. But in over three thousand years the slight,
slow wobbling of the earth on its axis had caused a shift. What was then
the North Star was now Thuban, in the constellation of Draco the Dragon.
The present North Star, Polaris, which is not exactly at the celestial
north pole, did not shine on the altar. Nor would the next star to
become the northern marker--bright Vega. But if the pyramids were still
standing after twenty-seven thousand years had passed, the cycle of
movement would be complete, and Thuban would again shine through the
channel to the altar of a forgotten Egyptian goddess.

It gave Rick a shiver to think about it. Even now, the pyramids were old
enough to have seen a change of north stars. They looked good for
another three thousand years or more. It would take a lot of time to
erode away that much massive stone.

Then he stopped thinking about it, because the telescope was in motion
again, and there was work to be done.

It was late night before the scientists were satisfied. The boys rode
back with Hassan, very thoughtful about the day's events. Now they had
both the little statue and the even greater mystery of the space signals
to think about.

Clearly, the strange signal was not of local origin. The scientists
rejected the idea that it came from trouble in the circuit. But it was
no natural heavenly object. What was it?

Tomorrow, Winston had said, they would decide on the next step. Right
now all hands were too tired to think clearly. The boys agreed that the
statement applied to them.

"Shall we eat?" Rick asked as they approached the hotel.

"Let's have a sandwich sent up," Scotty suggested. "I don't feel like
waiting in a dining room, even if one is open this late."

"Good idea." Rick leaned forward and told Hassan, "Just drop us off,
then go on home and get some rest."

"Not tired," Hassan said cheerfully. "You work, I rest."

They certainly were not working Hassan very hard, Rick agreed. But he
was pleasant to have around. They bade him good night in front of the
hotel and went for their room key. The clerk handed Rick an envelope
along with it. It was addressed to Mr. R. Brant, care of the hotel, and
the return address was in Arabic.

Rick waited until they were in their room to open it.