"Observing the positions of the sun and moon, and of certain stars with relation to each other. That is done with the quadrant and sextant; and then they use a chronometer, or clock, that tells exactly what the time is at Greenwich. Then, you see, this book is full of figures that look like multiplication-tables; and with these figures they 'work out their position;' that is, they find out where they are. Greenwich is near London, and all the tables are calculated from there."
"But suppose a sailor was dropped down here suddenly, without knowing what ocean he was in; could he find out where he was without anybody telling him?"
WORKING UP A RECKONING.
"Certainly; with the instruments I have named, the tables of figures, and a clear sky, so as to give good observations, he could determine his position with absolute accuracy. He gets his latitude by observing the sun at noon, and he gets his longitude by the chronometer and by observations of the moon. When he knows his latitude and longitude, he knows where he is, and can mark the place on the map."
Fred opened his eyes with an expression of astonishment, and said he thought the science of navigation was something wonderful.
The others agreed with him; and while they were discussing the advantages which it had given to the world, there was a call that sent them on deck at once.
"Land, ho!" from the lookout forward.
"Land, ho!" from the officer near the wheel-house.