"And so she would certainly be wrecked," said Rollo.
"No, not certainly," replied the captain. "As soon as they found that the water was shoaling, they would anchor."
"How do they know when the water is shoaling?" asked Rollo.
"By the lead," replied the captain. "Did you never sound with the lead and line?"
"No, sir," replied Rollo.
"Well, they have a lead, and a long line," rejoined the captain, "and they let the lead down to the bottom by means of the line, and so learn how deep the water is. The lead is round and long. It is about as large round, and about as long, as Jennie's arm, from her elbow to her wrist, and there is a small cavity in the lower end of it."
"What is that for?" asked Rollo.
"That is to bring up some of the sand, or mud, or gravel, or whatever it may be, that forms the bottom," replied the captain. "They put something into the hole, before they let the lead down, to make the sand or gravel stick. When they see the nature of the bottom in this way, it often helps them to determine where they are, in case it is a dark night, or a foggy day, and they have got lost. It is very easy to measure the depth of the sea in this way, where it is not over a few hundred fathoms."
"How much is a fathom?" asked Rollo.
"Six feet," replied the captain; "that is as far as a man can reach by stretching out both hands along a wall. If the water is only a few hundred fathoms deep," continued the captain, "we can sound; but if it is much deeper than that, it is very difficult to get the lead down."