Presently they came, as they had expected, to a floating boom, composed of logs of timber chained together. Here the piece of timber came to a standstill. No talk was necessary, as the course under these circumstances had been already agreed to. The petards and other objects were placed on the boom, upon which Rupert, as the lightest of the party, crept, holding in his hand a cord fastened round the log. Hugh and Gerald Dillon now climbed upon one end of the log, which at once sank into the water below the level of the bottom of the boom, and the current taking it, swept it beneath the obstacle. Rupert's rope directed its downward course, and it was soon alongside the boom, but on the lower side.

The petards were replaced, and the party again proceeded; but now Hugh swam on his back, holding a short rope attached to one end, so as to keep the log straight, and prevent its getting across the mooring chains of the boats forming the bridge; while Rupert and Gerald, each with a rope also attached to the log, floated down some ten or twelve yards on either side of the log, but a little behind it. The plan answered admirably; the stream carried the log end-foremost between two of the boats, which were moored twelve feet apart, while Gerald and Rupert each floated on the other side of the mooring chains of the boats; round these chains they twisted the ropes, and by them the log lay anchored as it were under the bridge, and between two of the boats forming it. If there were any sentries on the bridge, these neither saw nor heard them, their attention being absorbed by the expectation of an attack upon the breaches of Fort Saint Michael.

The party now set to work. With the gimlet holes were made a couple of feet above the water. In them the hooks were inserted, and from these the petards were suspended by ropes, so as to lie against the sides of the boats, an inch only above the water's level. The fuses were inserted; and all being now in readiness for blowing a hole in the side of the two boats, they regained the log, and awaited the signal.

The time passed slowly; but as the church clocks of the town struck eleven, a sudden outburst of musketry broke out round Saint Michael's. In an instant the cannon of the fort roared out, the bells clanged the alarm, blue fires were lighted, and the dead silence was succeeded by a perfect chaos of sounds.

The party under the bridge waited quietly, until the noise as of a large body of men coming upon the bridge from the town end was heard. At the first outbreak Gerald Dillon had, with some difficulty, lit first some tinder, and then a slow match, from a flint and steel--all of these articles having been most carefully kept dry during the trip, with the two pistols, which were intended to fire the fuses, should the flint and steel fail to produce a light.

As the sound of the reinforcements coming on to the bridge was heard, Gerald Dillon on one side, Rupert Holliday on the other, left the log, and swam with a slow match in hand to the boats. In another instant the fuses were lighted, and the three companions swam steadily downstream.

In twenty seconds a loud explosion was heard, followed almost instantaneously by another, and the swimmers knew that their object had been successful, that two of the boats forming the bridge would sink immediately, and that, the connexion being thus broken, no reinforcements from the town could reach the garrison of the Fort Saint Michael. Loud shouts were heard upon the bridge as the swimmers struck steadily down stream, while the roar of the musketry from Fort Saint Michael was unremitting.

Half an hour later the three adventurers landed, at a point where a lantern had, according to arrangement, been placed at the water's edge by Pat Dillon, who was in waiting with their clothes, and who received them with an enthusiastic welcome. Five minutes later they were on their way back to their camp.

In the meantime the battle had raged fiercely round Fort Saint Michael. The attack had been made upon two breaches. The British column, headed by the grenadiers, and under the command of Lord Cutts, attacked the principal breach. The French opposed a desperate defence. With Lord Cutts as volunteers were Lord Huntingdon, Lord Lorn, Sir Richard Temple, and Mr. Dalrymple, and these set a gallant example to their men.

On arriving at a high breastwork, Lord Huntingdon, who was weakened by recent attack of fever, was unable to climb over it.