"We know more than that," Foster said. "He mentions a plain; and it must lie on a continent to the east--" "If you assume that he sailed from Europe to America, then the continent to the east would be Europe," I said. "But maybe he went from Africa to South America, or--" "The mention of Northern sailors--that suggests the Vikings--" "You seem to know a little history, Foster," I said. "You've got a lot of odd facts tucked away." "We need maps," Foster said. "We'll look for a plain near the sea--" "Not necessarily." "--and with a formation called a chalk face to the east." "What's this 'median line' business mean?" I said. "And the bit about ten thousand parts of something?" "I don't know," Foster said. "But we must have maps." "I bought some this afternoon," I said. "I also got a dime-store globe. I thought we might need them. What the hell! let's get out of this and back to the room, where we can spread out. I know it's a grim prospect, but...." I got to my feet, dropped some coins on the table, and led the way out. * * * * * It was a short half block to the flea trap we called home. The roaches scurried as we passed up the dark stairway to our not much brighter room. I crossed to the bureau and opened a drawer. "The globe," Foster said, taking it in his hands. "I wonder if perhaps he meant a ten-thousandth part of the circumference of the earth?" "What would he know about--" "Disregard the anachronistic aspect of it," Foster said. "The man who wrote the book knew many things. We'll have to start with some assumptions. Let's make the obvious ones: that we're looking for a plain on the west coast of Europe, lying--" He pulled a chair up to the scabrous table and riffled through to one of my scribbled sheets: "50/10,000s of the circumference of the earth--that would be about 125 miles--west of a chalk formation, and 3675 miles north of a median line...." "Maybe," I said, "he means the Equator." "Certainly," Foster said. "Why not? That would mean our plain lies on a line through--" he studied the small globe. "Warsaw, and south of Amsterdam." "But this bit about a rock out-cropping," I said. "How do we find out if there's any conspicuous chalk formation there?" "We can consult a geology text," Foster said. "There may be a library nearby." "The only chalk deposits I ever heard about," I said, "are the white cliffs of Dover." "White cliffs...." We both reached for the globe at once. "125 miles west of the chalk cliffs," Foster said. He ran a finger over the globe. "North of London, but south of Birmingham. That puts us reasonably near the sea--" "Where's that atlas?" I said. I rummaged, came up with a cheap tourists' edition, flipped the pages. "Here's England," I said. "Now we look for a plain." Foster put a finger on the map. "Here," he said. "A large plain--called Salisbury."