The table gave part of the answers for a whole series of right-angled triangles. To discover the range of a French 36-gun frigate it was only necessary to use a sextant or quadrant to measure the angle made by, say, the mainmasthead. The height was known from the table and became the given side of a triangle - the vertical side, whereas the base was the unknown quantity, the distance or range. With the angle which had just been measured, the base could be worked out quickly and was, of course, the range.

Measuring the height of another ship's masts was a familiar enough exercise: when sailing in company and ordered to keep a certain distance, the officer of the deck used sextant or quadrant to measure the angle made by the mainmasthead and, knowing what it should be if they were the correct distance, could see that if the angle was too small they were too far away and if too large they were too near. And, of course, measuring the masthead angle was very useful when chasing an enemy ship: the slightest change in the angle indicated which was gaining.

This time though, providing all went according to plan, Southwick had done the sums, so that the table included the particular angles of a French 36-gun frigate like the Calypso for the cap of the mainmast and maintopmast, and the foreyard, the foretop and cap of the foretopmast, at a range of 2,000 yards. All the officers had worked at their tables and checked the figures. They found that the old master had not made a mistake. Ramage had not expected that he would, but he noticed from the hurried scribbling that Kenton and Orsini had made errors and then rapidly corrected them.

Two thousand yards... He considered the figure; spoke it to himself and then imagined it written down, first in his own handwriting and then in type as the figure appearing in a set of tables. The first gamble was with figures. The second gamble was that the three French frigates would be secured stern to the quay at such an angle that their broadside guns could not possibly fire through the entrance. He would win that round if they were able to fire only their bow-chase guns, one each side and no bigger than 12-pounders. Six altogether, with a range of 1,800 yards at six degrees of elevation with a 4-pound charge of powder. At that range a French gunner, or any other, for that matter, would be lucky to be able to bowl a shot through the harbour entrance if his ship was anchored 1,800 yards outside, so there was not much risk from the bow-chase guns. Or from the other guns at that range, really, unless one of the frigates managed to slew round and fire off a broadside. Then there would be eighteen roundshot ricocheting off the water, and some might hit, much as a sportsman (poacher, more likely) would fire a shot into the middle of a rising covey in the hope of bringing down a single bird.

No, he corrected himself, the biggest gamble, although still concerning the 2,000 yards, was on the forts. There were two of them, Monte Filippo on the north side and high up, and Santa Catarina low down at the entrance. A third one at the southern entrance was not really a fort; simply a series of gun positions at the end of a short headland known as La Rocca and protected by stonework.

There might be 32-pounders up there in Monte Filippo, and with a 10-pound charge they could fire a shot 2,900 yards. It would be plunging fire, and at extreme range. Ricochets were always wildly inaccurate with plunging fire, bouncing all over the place. When a gun was firing on an almost level plane - from one ship at another, for instance - ricochets were often quite accurate; the first graze, as it was called, could be at a third of the extreme range . . .

How often were the crews of any guns in Monte Filippo likely to be exercised? Were the gun platforms made of wood, which might have rotted? Was there wooden planking laid over stone? Or just smooth stone? Were the French gunners up in the forts conscientious men who looked after the guns, kept the powder dry, and tended the shot, keeping them well painted and making sure they did not bulge with rust flakes? Was the ropework sound, or had it gone grey, rotting in the rain and sun, so that train tackles and breechings would be useless, parting with the recoil of the first round and letting the gun career back out of control?

Questions but no answers. Was there even a garrison in either fort? Why would the French bother, because Porto Ercole was now a port of no significance whatsoever, just a haven for fishing boats, not a port used to supply any town except perhaps Orbetello, whose wants must be slight and which probably relied on Santo Stefano. Santo Stefano - when he and Jackson had sneaked in there several years ago to rescue Gianna they had checked up on its great fort and found out the size of the guns, 32-pounders, and the fact that the gunners never fired them in practice.

One thing is certain, he told himself brutally, it is far too late to worry now; the Brutus and the Fructidor have their orders. They know the whole objective is so important that even if the forts are crammed with France's most skilled artillerymen and bristling with excellent guns, the bomb ketches must carry out their orders, or sink in the attempt. You sent 'em; you get the credit if they succeed; you get the blame if they fail.

Aitken was shouting orders. Idly Ramage watched black figures swarming sure-footed up the ratlines of the mainmast in the darkness the moment Aitken bellowed: "Away aloft!"

After that there was a stream of orders aimed at the men on the maintopsail yard, Aitken's mild Scottish accent amplified and distorted by the speaking trumpet: "Trice up ... lay out!" The men triced up the studdingsail booms out of the way, and then scrambled out along the yard.

"Man the topsail sheets!" This was directed to the men down on deck, and then the speaking trumpet was aimed aloft again. "Let fall!"

The topmen, who had already begun to loosen the knots of the gaskets in anticipation of the order, knowing that they could not be seen from the quarterdeck and anxious to save a few seconds, untied the strips of canvas and the sail unrolled, a great canvas sheet which hissed and scraped in the quiet night as it flopped like a curtain before the wind had a chance to fill it.

"Sheet home!" Aitken shouted across the deck, and then to the men aloft: "Lower booms!" The studdingsail booms were lowered back into place, and Aitken followed that with the final order to the topmen: "Down from aloft!"

There were still more orders for the men on deck. "Man themaintopsail halyards - now then, haul taut!" That took up the slack ready for the next string of orders. "Tend the braces there, and now, all together, hoist the maintopsail!"

As the yard was trimmed sharp up the Calypso began to forge ahead, slowly standing in towards Talamone, on the mainland, as the quartermaster brought the ship as close to the wind as she would sail with only one topsail. Then the mizentopsail was let fall and sheeted home and, as the jibs were hoisted, the foretopsail was let fall and the Calypso, gathering speed, sailed closer to the wind.

"We'll tack about a mile off Talamone," Ramage said. "Then if anyone in Santo Stefano saw us get under way, they'll assume we're heading up to the north, unless they have the patience to continue watching . . ."

"We'll give the fishermen a scare," Aitken commented because the Calypso was now heading within a point or two of the light of the fishing boat which had been on the mainland side of the bay for the past few hours.

"They'll know we can see them," Ramage said. "Anyway, they're probably asleep, with their lines hitched round their big toes so that they feel the twitch the minute a fish bites."

He bent down over the binnacle and looked at the weather side compass. The Calypso was comfortably laying a course of north-east, so the wind must be about north-west by north. They would clear Punta Lividonia on the next tack and then slowly bear away as they sailed down the west side of Argentario with a soldier's wind. The stars were bright enough to make the land clear; there was nothing to do now but wait - for almost twelve hours. The Calypso under topsails alone was, in this breeze, almost as much trouble to handle as a rowing boat. . .