Frantically he stopped that line of thought.
He hauled out a sheaf of maps. He had come prepared. He had brought the duplico-camera, the film developing equipment, the pantograph, other odds and ends. He had a shelf-full of celestial mechanic manuals, as well as books on the more ordinary arithmetics.
But he had had only one year of math. Somewhere along the line, he had outguessed his patriarch of a father and his matriarch of a mother: law had been the result.
Well suited, he had felt at the time, to the trickery, the deceit, and the orneriness of the typical Unterzuyder mind!
Anyway, he needed a slide-rule before he could tackle the equations. For the present, he would work out the date the map was made. Then it would be possible to discover X's present position.
All that was necessary was, mathematically, to rotate the present-time position of the planets backward in time—clockwise, that is—until they coincided with map-position.
The star-maps, the Emphemeris, and the Planet Catalogue should make that fairly simple.
After an hour, his nerves began to quiver. He ran his hands distractedly through his awry blonde hair. He had the answer. And it was impossible. Except that it was correct.
Apparently, the map had been drawn up in prehistoric times.
50,000 years ago!