Dr. Staines got from the carpenter some sheets of zinc and spare copper, and some flannel:  these he cut into three-inch squares, and soaked the flannel in acidulated water.  He then procured a quantity of bell-wire, the greater part of which he insulated by wrapping it round with hot gutta percha.  So eager was he, that he did not turn in all night.

In the morning he prepared what he called an electric fuse—­he filled a soda-water bottle with gunpowder, attaching some cork to make it buoyant, put in the fuse and bung, made it water-tight, connected and insulated his main wires—­enveloped the bottle in pork—­tied a line to it, and let the bottle overboard.

The captain and officers shook their heads mysteriously.  The tars peeped and grinned from every rope to see a doctor try and catch a shark with a soda-water bottle and no hook; but somehow the doctor seemed to know what he was about, so they hovered round, and awaited the result, mystified, but curious, and showing their teeth from ear to ear.

“The only thing I fear,” said Staines, “is that, the moment he takes the bait, he will cut the wire before I can complete the circuit, and fire the fuse.”

Nevertheless, there was another objection to the success of the experiment.  The shark had disappeared.

“Well,” said the captain, “at all events, you have frightened him away.”

“No,” said little Tadcaster, white as a ghost; “he is only under water, I know; waiting—­waiting.”

“There he is,” cried one in the ratlines.

There was a rush to the taffrail—­great excitement.

“Keep clear of me,” said Staines quietly but firmly.  “It can only be done at the moment before he cuts the wire.”

The old shark swam slowly round the bait.

He saw it was something new.

He swam round and round it.

“He won’t take it,” said one.

“He suspects something.”

“Oh, yes, he will take the meat somehow, and leave the pepper.  Sly old fox!”

“He has eaten many a poor Jack, that one.”

The shark turned slowly on his back, and, instead of grabbing at the bait, seemed to draw it by gentle suction into that capacious throat, ready to blow it out in a moment if it was not all right.

The moment the bait was drawn out of sight, Staines completed the circuit; the bottle exploded with a fury that surprised him and everybody who saw it; a ton of water flew into the air, and came down in spray, and a gory carcass floated, belly uppermost, visibly staining the blue water.

There was a roar of amazement and applause.

The carcass was towed alongside, at Tadcaster’s urgent request, and then the power of the explosion was seen.  Confined, first by the bottle, then by the meat, then by the fish, and lastly by the water, it had exploded with tenfold power, had blown the brute’s head into a million atoms, and had even torn a great furrow in its carcass, exposing three feet of the backbone.