"Look there!" he exclaimed, but it was too late. "I'll swear to it I saw the Half Moon, Hudson's ship," he declared excitedly. "We're way back now, and don't seem to be slacking up, either."
Estelle came to the window by his side. The rapidly changing scene before her made her gasp. It was no longer possible to distinguish night from day.
A wavering streak, moving first to the right and then to the left, showed where the sun flashed across the sky.
"What makes the sun wabble so?" she asked.
"Moving north and south of the equator," Arthur explained casually. "When it's farthest south—to the left—there's always snow on the ground. When it's farthest right it's summer. See how green it is?"
A few moments' observation corroborated his statement.
"I'd say," Arthur remarked reflectively, "that it takes about fifteen seconds for the sun to make the round trip from farthest north to farthest south." He felt his pulse. "Do you know the normal rate of the heart-beat? We can judge time that way. A clock will go all to pieces, of course."
"Why did your watch explode—and the clock?"
"Running forward in time unwinds a clock, doesn't it?" asked Arthur. "It follows, of course, that when you move it backward in time it winds up. When you move it too far back, you wind it so tightly that the spring just breaks to pieces."
He paused a moment, his fingers on his pulse.