Henry looked overhead. “I see nothing but the sun,” he said.
“That’s all a navigator needs to see,” laughed the captain. “It’s just as I told you. As long as he can see the sun, or the stars, you can’t lose him. When he looks at either through a sextant, he can tell exactly where he 1s.”
“I see,” said Henry. “The sun tells you your latitude and longitude.”
“Correct. That dot on the chart,” and the captain pointed with his pencil, “is the spot where this derelict was reported to be. Also it’s just where we are now. If I drew a mark from that dot along the direction in which the wind is blowing, which is from the southwest, that should be the course of the derelict. But the current may have carried it to right or left of that line. So we have to make a grid, in order that we may not pass the derelict in our search. We will sail a course that takes us first to right and then to left of this supposed course, in such a way that we can examine every foot of the sea over a wide area. Our present grid will be like this;” and the captain drew on a piece of paper a diagram something like the following:
