Mark heaved a sigh, but it was one full of satisfaction as they two sat quietly talking together, with first one and then another to come up and utter a few words of congratulation; and when sailors and marines passed and saluted with a friendly smile, there was no mistaking the popularity of the two convalescents. Meanwhile the _Nautilus_ glided along due south, and there was a good deal of speculation as to her next destination, till Mr Staples came up, and in the conversation which ensued, announced that they were to search for a river about sixty miles along the coast, one which was not marked down in any chart, but was supposed to exist, and to be a stronghold of those engaged in the slave trade. It was getting toward evening, and the two invalids had pleaded for the doctor's permission to stay longer on deck, for the soft air was delicious, and gave them fresh strength at every breath. They were very silent as they sat watching with keen delight the varied business of the ship, doubly interesting to them now that they could not take part in it, when the wind began to drop, and the course of the vessel to grow more sluggish. There was nothing for the men to do, and permission had been given to a party of them, just towards sundown, to take the grains forward and try to harpoon some of the swift fish playing about their bows in the golden water; but instead of going and perching himself somewhere to take part in the sport, Bob Howlett hung about the chair of his brother middy. "Why don't you go and join in the fishing, Howlett?" said Mr Russell. "Oh, I don't know," he said. "It'll be quite dark directly, and I was wishing, sir, for something to happen to make me an invalid." "Because you have such an affection for Doctor Whitney's doses?" said Mark, laughing. "No, so you needn't make nasty remarks," replied Bob. "I thought so, because middies who have been a little out of sorts get all kinds of attentions, and those who are quite well get bullied by first lieutenants, and are spoken to by captains as if they weren't worth their salt, as Mr Staples calls it." "I shall have to report Mr Robert Howlett's insubordinate language," said Mark's fellow-invalid, when all at once there came a cry of rage, followed by a loud shouting somewhere forward. Then more cries, and confusion, and directly after there was a desperate scuffle going on by the forecastle hatch. "What's that?" cried the first lieutenant; and in a few minutes, after a desperate fight, the two blacks were dragged forward, pushed by four of the men, and held by main force while the captain, who had hurried on deck, called for an explanation. This was given by a dozen voices at once, but in obedience to a command there was silence, in which the heavy panting breathing of the blacks could be plainly heard. "Now then," said the captain, "one man speak. You, Dance, step forward. What does this mean?"