His eldest brother, in a burst of enthusiasm, had said he could borrow his gun and have some heavy shot so that he could try for a duck or two. Early on Sunday, the Medway still misty and the sun not yet up, he had rowed out, passing the old and new ships of the line, frigates and transports lying on moorings, and the ancient forts of red brick and of grey stone. He had planned to start off just before the top of the tide and carry the ebb all the way, resting to eat his bread and cheese at slack water, and start back with the first of the flood. And that was what he had done. He had rowed along the high-banked channels of the saltings and often let the ebb drift the boat along - so that it slowly grounded a few yards from some ducks dabbling away, tails in the air, in their eternal hunt for food. Slowly he had collected his trophies - the banks seemed to muffle the heavy blam of the gun firing, so that within fifteen minutes or so ducks had settled again. By the time the flood took him back to Hoo he had seven plump duck lying on the bottom boards, and a heap of fresh sea kale to go with them. His eldest brother's only comment as he took the gun back was that he might have plucked the birds while he waited for the tide to turn ...

Although he had enjoyed rowing his skiff, he had found equal pleasure in going over the slight rise of hill to Hoo church on a Thursday afternoon to hear the organist practising for the Sunday service: there he had discovered his love for music. The organist, at first surprised and then pleased to find the young boy always sitting quietly at the back of the church, had taught him to read music and, guessing he would go to sea as soon as he was old enough, suggested that the flute was the instrument for him to learn. They had discussed the violin - but varying climates and long voyages, humidity and high temperatures would warp the wood and snap the strings, and he would never be able to carry enough as spares. The flute was small, easily carried, durable and, more important, it made pleasing music, So he had learned the flute and he had gone to sea ... and here he was standing on the quarterdeck of a French bomb ketch, a commission officer by the age of twenty-three.

More important was the fact that he was one of Captain Ramage's officers. Few captains had had more of their actions described in the London Gazette, and in his imagination Martin saw himself back in the old house at Hoo, his father listening to his exploits, and he would be able to say casually, for the benefit of his brothers, and with an airy wave of the hand: "But you probably read about that in the Gazette ..."

Martin glanced round the Brutus'sdeck and saw that his half dozen men had done everything possible to tidy up the ketch, given that the first lieutenant had forbidden any scrubbing or polishing of the corroded brasswork with brick dust. That was a clear indication that Captain Ramage intended to scuttle or burn both ships, and although it was disappointing for a young lieutenant who could reasonably have expected to be given the command if the Brutus was being sent back to Gibraltar as a prize, it made sense. There were so many French ships about these days that they would be lucky to cover five hundred miles before being captured . . .

On the other side of the Calypso, whose gun port lids were still closed and whose guns had their muzzles sealed by tompions with canvas covers, or aprons, over the flintlocks to keep out the damp of the night, the Fructidor was a ship of frustration as far as Paolo Orsini, a midshipman in the Navy of His Britannic Majesty, was concerned. His half dozen men, working under Thomas Jackson, had sluiced the decks with the only deck-wash pump in the ship, one whose leathers were shrunk and splitting from disuse and needed wiping carefully with tallow before they could be induced to suck, let alone pump. They had coiled all the falls of the halyards, and then whipped some ropes' ends. More tallow had been wiped into the pawls of the windlass; a bored William Stafford had worked a couple of Turk's heads on the tiller using line he had found in the French bosun's store. That was all Mr Aitken would allow; he said it was a waste of time and effort to do anything else with the ships.

Paolo put down his telescope by the binnacle and walked to the forward mortar. It was a strange weapon - so stubby, like a cannon with most of the barrel sawn off, and the trunnions at the breech. The inside of the barrel, the bore (the first section into which the shell was slid), was like the inside of a bottle with its bottom knocked off to form the muzzle. The gunner said the gun was the equivalent of the British 10-inch sea service mortar, and certainly with a muzzle ten inches in diameter it was a formidable-looking weapon. He peered down the bore and could just see where it narrowed into the chamber at the bottom, like the neck of a bottle. That held the gunpowder charge which would launch the mortar shell into the great parabola that should end on the enemy's head.

The whole mortar was fitted on to something that could be mistaken for a solid cartwheel lying on its side. He had been down below and seen how this great wheel - in effect the base -was supported by under-deck stanchions which spread the weight of the mortar and the shock of its recoil over several extra floors and stringers, and the deck beams were twice as thick as normal.

The "cartwheel" had the mortar bed resting on it. This was a thick but flat rectangular wooden block with a hole in the middle of the underside. This fitted on to what would be the hub if the base had been a real wheel. A thick pintle or axle dropped down into a hole that went through the bed and into the base, so that the bed could revolve and the mortar be aimed.

The mortar was almost obscene, Paolo thought, like a fat and short pig that could only grunt. It was a stubby cast-iron pot with short, solid trunnions sticking out sideways at the bottom which acted as the axle when the gun was elevated. The trunnions were held down by metal clamps (called "cap squares", although they were semi-circular) which stopped the mortar running wild when it fired,.

The piece of timber which could slide back and forth in the slot under the mortar, and which had a saucer-like depression where the underside of the mortar barrel rested, was called the bed bolster. You levered up the muzzle with handspikes until it was at the right elevation, then you pulled on the two ropes and slid the bed bolster underneath until the barrel was supported. After that he was not sure what happened, so he had borrowed the gunner's notebook, although the handwriting was very difficult to read. He sat down on the mortar bed and concentrated.

He had not been reading for more than ten minutes when Thomas Jackson came along and inspected the gun.

"Looks as though it'd go right through the deck the first time you fired it," the American commented. "Still, there are three hundred shells for this one, and three hundred for the other -" he gestured aft to the other mortar. "The French presumably had faith in it."

Paolo looked at the sandy-haired, thin-faced American, and his jaw dropped with dismay. "Do you mean you wouldn't want to fire this if the captain gave you permission?"

"I'd sooner he gave me a direct order, sir," Jackson grinned, teasing the boy. "I've never had anything to do with these things. Always fired guns that shot horizontally. This is more like tossing a grenade over a wall and hoping to hit something you can't see."

"Exactly!" Paolo exclaimed. "You can't do that with an ordinary gun. If your enemy is behind the thick walls of a castle, or on the other side of the hill, you can't attack him with a cannon because it fires straight - more or less straight, anyway. With the mortar you can hurl shells down on him. Explosive shells."

"Yes," Jackson agreed as Stafford and Rossi walked up to listen to the conversation, "but the fuse that makes the shell explode inside the enemy's walls might also make it burst inside the mortar before you can fire it."