When little Jacob and little Sol came on deck they saw three ships, going the other way. They wondered what they were, and they asked the mate. And the mate smiled and said that two of the ships were Dutch and he supposed that they were going to Batavia. And he thought that the other ship was American and he hoped that it would take the letters they had left at Anger. Little Jacob hoped that it would; but little Sol didn't seem to care. And, all of that day, they watched for more ships, and they saw land, now and then, far off on the horizon. It was very hot, for they were almost at the equator; so that even little Sol was contented to keep still. And, towards night, they saw one of the sailors getting the lead line ready.
The lead is just a big lump of lead, like a sinker that is used on a fishing line, and it is tied to the end of a long line that has the fathoms marked on it in much the same way that the log line has the knots marked; but the marks on the lead line are really six feet apart. And the lead itself has the lower end just a little bit hollowed. The sailor who was getting it ready first made sure that the line was all clear, without any knots or kinks in it. And, when he had seen that the line was all right, he took up the lead and smeared some grease on the bottom of it. The sailor was the old man who had given little Jacob the model of the brig.
Little Jacob was surprised. "What is that?" he asked. "Is it grease?"
The sailor was amused. "It's grease," he said, "sure enough."
"And what is it for?" asked little Jacob again. "I hope you don't mind telling me."
"No, lad," said the sailor. "Be sure I'll tell you. It's to bring up some of the bottom so's the cap'n can tell where we are."
Little Jacob didn't understand. "I don't see," he said, "how Captain Solomon can tell where we are, that way."
The sailor laughed. "Well, no," he said. "I s'pose you don't. Well, it's this way. The bottom of the sea is different in different places. In some parts it's mud and in other parts it's gray sand and in others it's black sand and in others yet it's yellow sand, and so on. In the deep oceans it's different yet, but no lead will reach it. And every good sailor man, such as Cap'n Solomon is, should know the bottom he'll find on the course he sails. And when I heave this lead, it tells him how much water he's got under him and the kind of bottom, for the lead brings up a little of the mud or the sand that sticks to the grease. That's how it is."
Little Jacob thought that he understood. "And will you heave the lead now?" he asked.
"I heave the lead when I'm ordered to," said the old man. "But I'm thinking the cap'n won't want it hove till after dark. There's no lights, hereabouts, you see. Lighthouses," he added, seeing that little Jacob didn't know what he meant.