The threshing and splashing of the fish had attracted the attention of a great flock of gulls as the boys headed the Katie once more toward the scene of activity; and in the bright sunlight, with the glinting slippery bodies of some of the threshers almost constantly visible, the spray flying, and the bead-eyed sea-birds fluttering and watching overhead, the picture was rather a thrilling one. They were both determined enough in their intentions, yet when they actually arrived upon the scene and a thresher of apparently abnormal size rushed to meet them with a resounding slap of his tail upon the surface of the water that sent the foam flying skyward and seemed like a laughing defy to their plans, even the cool-blooded Walter began to feel a little excitement.

This selfsame thresher lost no time in making good his challenge, but swallowed the bait, and ran off with it away to windward so rapidly that it seemed as if he were going to tow the boat, which was again got full and by on the port tack. Walter was now paying out the line as slowly as he could, with a turn under a belaying-pin, as he made the first remark recorded in this sketch. But it soon became evident that something would have to be done if they did not wish to be towed to sea, so Harry ported his helm to let the boat fall off and endeavor to check the creature in its mad career. As the wind came more abeam, however, so did the shark, and instead of making leeway, the attraction to windward was so powerful that the situation looked almost dangerous, and as if the only way to counteract the shark's tow-line was to let it over the stem with a free sheet. It was just a question, however, whether even then the boat might not be drawn astern, and Walter was actively considering the advisability of cutting the line, when all at once the fish took a turn and once more made toward them.

"Head her up again, quick!" shouted Walter. "Down your helm. He's coming!"

The boat had fortunately way enough to bring her quickly up into the wind as Harry shoved his tiller hard over to starboard and hauled in his sheet, then jumped to help his friend get in the slack of the line as the infuriated monster dashed toward them. He was not a moment too soon. Had the boat not changed direction and forged ahead a little the wildly rushing thresher would have struck it a terrific blow on the port-quarter. As it was, he passed the boys with a leap clear out of water that sent a tremendous splash of spray in their faces, and just missed the boom as he dived astern. It was a thrilling moment; but, indeed, the whole affair, from the time the shark first swallowed the bait, seemed to have happened in less time than one could tell it.

"By jingo!" cried Walter. "What's he going to do next?"

They had not long to wait for a reply. Circling around to seaward, the thresher repeated exactly the same manœuvre, this time a streak of bloody foam following in his wake. The boys had all they could do to handle the boat in consonance with the shark's movements. As he madly rushed ahead, the line began to smoke from its friction with the rail at the velocity it paid out, and Harry again had to leave his helm to bail water and pour it upon the hempen coils, so quickly snaking out, with the threat of possible disaster when the tub should be emptied. Walter's hands were burned and blistered and raw in spots from contact with the flying line, in a vain endeavor this time to grasp it and get a turn around a pin. The fish went too fast. The boys looked at each other, too excited to speak, as they glanced at the rapidly emptying tub and the flying streak of blue foam ahead. Another instant and the line was all paid out. The last coil of it swirled over the side as they both grasped the tub with all their might to see if they could hold it. The end of the line was made fast to the tub. It might have been a dangerous thing to do, for if the line had parted under the strain, and hit one of them a blow with its rebounding end, it would have been a severe one. But fortunately this shark felt the check, and with a mighty splash he turned again and made back towards them.

"Haul in and coil down for all you're worth!" commanded Walter, as he heaved a sigh of relief, and applied his bleeding hands vigorously to getting the slack of the line inboard again.

The shark did not come toward them so directly as before, and the boat had not so much way on, so that they were able to finally get the line taut and a turn taken beneath a pin again. The strain was maintained anxiously for a few minutes, when the thresher took another sudden rush for their port-quarter. With all the vigor acquired by his momentary rest he leaped again clear out of water, and as the boys rapidly hauled in the line a strange thing happened. The strain came suddenly upon the leaping thresher, and brought such a snapping jaw upon his jaws that he actually turned a complete somersault in the air before he sank again beneath the surface astern, and as the line paid out once more the sweat streamed from the faces and bodies of the daring fisher-lads.

"We can't keep this up," said Walter, as he hugged his sore hands.

"What can we do?" questioned Harry.