For a week Crab K towed steadily to the south this blazing and thundering marine citadel; and then the crab signalled to the still accompanying repeller that it must be relieved. It had not been fitted out for so long a cruise, and supplies were getting low.

The Syndicate, which had been kept informed of all the details of this affair, had already perceived the necessity of relieving Crab K, and another crab, well provisioned and fitted out, was already on the way to take its place. This was Crab C, possessing powerful engines, but in point of roof armour the weakest of its class. It could be better spared than any other crab to tow the Adamant, and as the British ship had not, and probably could not, put out another suspended cannon, it was considered quite suitable for the service required.

But when Crab C came within half a mile of the Adamant it stopped. It was evident that on board the British ship a steady lookout had been maintained for the approach of fresh crabs, for several enormous shell and shot from heavy guns, which had been trained upward at a high angle, now fell into the sea a short distance from the crab.

Crab C would not have feared these heavy shot had they been fired from an ordinary elevation; and although no other vessel in the Syndicate's service would have hesitated to run the terrible gauntlet, this one, by reason of errors in construction, being less able than any other crab to resist the fall from a great height of ponderous shot and shell, thought it prudent not to venture into this rain of iron; and, moving rapidly beyond the line of danger, it attempted to approach the Adamant from another quarter. If it could get within the circle of falling shot it would be safe. But this it could not do. On all sides of the Adamant guns had been trained to drop shot and shells at a distance of half a mile from the ship.

Around and around the mighty ironclad steamed Crab C; but wherever she went her presence was betrayed to the fine glasses on board the Adamant by the bit of her shining back and the ripple about it; and ever between her and the ship came down that hail of iron in masses of a quarter ton, half ton, or nearly a whole ton. Crab C could not venture under these, and all day she accompanied the Adamant on her voyage south, dashing to this side and that, and looking for the chance that did not come, for all day the cannon of the battle-ship roared at her wherever she might be.

The inmates of Crab K were now very restive and uneasy, for they were on short rations, both of food and water. They would have been glad enough to cast loose from the Adamant, and leave the spiteful ship to roll to her heart's content, broadside to the sea. They did not fear to run their vessel, with its thick roofplates protected by spring armour, through the heaviest cannonade.

But signals from the repeller commanded them to stay by the Adamant as long as they could hold out, and they were obliged to content themselves with a hope that when night fell the other crab would be able to get in under the stern of the Adamant, and make the desired exchange.

But to the great discomfiture of the Syndicate's forces, darkness had scarcely come on before four enormous electric lights blazed high up on the single lofty mast of the Adamant, lighting up the ocean for a mile on every side of the ship. It was of no more use for Crab C to try to get in now than in broad daylight; and all night the great guns roared, and the little crab manoeuvred.

The next morning a heavy fog fell upon the sea, and the battle-ship and Crab C were completely shut out of sight of each other. Now the cannon of the Adamant were silent, for the only result of firing would be to indicate to the crab the location of the British ship. The smoke-signals of the towing crab could not be seen through the fog by her consorts, and she seemed to be incapable of making signals by sound. Therefore the commander of the Adamant thought it likely that until the fog rose the crab could not find his ship.

What that other crab intended to do could be, of course, on board the Adamant, only a surmise; but it was believed that she would bring with her a torpedo to be exploded under the British ship. That one crab should tow her away from possible aid until another should bring a torpedo to fasten to her stern-post seemed a reasonable explanation of the action of the Syndicate's vessels.