'Now, as we've come south and into this good weather, just look: the sea is adeep blue, the sky an exciting blue, the trade wind clouds are just the funny shapes you predicted.'

Ramage had earlier tried to describe the day's routine at sea in the Tropics but Wilkins, looking at the Channel off Ushant, had not really believed him. The day, Ramage had predicted, would begin with dawn revealing a band of cloud on the eastern horizon which, as the sun was behind it, would be menacing. Then, as the sun climbed higher the band would disappear and the sky clear.

By nine or ten o'clock, there would be an occasional tiny cloud, like white blanket fluff; within half an hour more would be gradually forming into narrow columns, like marching men, and all borne westward by the trade wind, which would be increasing as the sun rose. Although it was an optical illusion the clouds would seem to be converging on a single point on the western horizon, and each would be changing shape until the underside was flat but the upper part would turn into a strange shape. To Ramage and to Wilkins when he first saw them they looked like the white alabaster effigies he had seen on tombs: a recumbent knight in armour, feet sticking up at one end, head complete with visor, at the other. There might be one which clearly represented a woman. Then Wilkins was spotting faces: just the profile staring up into the sky as though its owner was lying flat on an invisible bed.

The first real day of trade wind clouds had Wilkins, the botanist Garret and Ramage vying with each other to spot and then identify the faces of well-known figures. Wilkins swore he could see the head of Sir William Beechey, the artist, but both Ramage and Garret protested they did not know what he looked like. They all agreed on the Prince Regent, followed ten minutes later by the bloated face of Dundas. Neither Ramage nor Wilkins could give a verdict on Garret's recognition of Arthur Young, the Secretary of the Board of Agriculture, but all three soon spotted Evan Nepean, the Secretary to the Board of Admiralty.

A delighted Wilkins then spotted Southwick's profile and the master, made to hurry on deck, claimed the cloud flattered him.

Wilkins, continuing his survey of the voyage so far through an artist's eyes, had one complaint. 'You say the sea and sky will get much more blue before we reach our destination, but who in England will believe me if I paint what I see now? I hadn't realized how few of my fellow artists ever travelled south of Rome - and many, like me, haven't been able to set foot on the Continent yet because of the war. I have seen many paintings of subjects like a "Frigate action off Martinique", or "The Battle of the Saints" - they are islands nearby, are they not? The sea and the sky look like the Channel or North Sea: look like the sea should look - or so I thought. Now I realize that those artists had never seen tropical seas and skies; they were painting actions as described by individual captains, who would make sure the naval details were correct - the position of ships, the rigging, and so on. But they never told the artists - or the artists would not believe - the colours. Why, just look at that row of fire buckets - have you ever seen polished leather look so rich in England? The canvas of the sails - white be damned; just look at how much raw umber and burnt sienna there is. I'll show you when I mix some colours.

'Gaudy, my dear sir, that's what the Tropics are, and I love them: colours are beginning to live!'

'For real colour you should see the West Indies,' Ramage said. 'The colour of the sea over a coral reef - light blue that seems alive, or a pale green like silk. The colours of the black women's dresses: they take three pieces of cloth of unbelievable gaudiness, put them on their bodies and on their heads, and seem more fashionable than milady riding in Rotten Row.'

Ramage was sitting at his desk looking through the journals kept by Kenton, Martin and Orsini. They were supposed to be diaries of happenings on board the ship, with navigational facts, descriptions of 'any unusual events' and sketches of any coasts the Calypso passed. Kenton and Martin were, for practical purposes, almost illiterate, and Orsini was lazy. Kenton and Martin had gone to sea at an early age; they could knot and splice, box the compass, load a cannon and fire a musket at an age when most boys on land were still scared of the dark, but they could not parse a sentence and even now would not know what to do with an adverb. Paolo's ruthless tutors at home in Volterra made sure he had a remarkable knowledge of grammar, so he spoke English, French and Spanish fluently, as well as Italian. This was normal for most intelligent aristocrats. Paolo's trouble was sheer laziness and almost anostalgie de la boue for the rougher side of seamanship. He preferred rope-work to navigation; he would sooner paint Stockholm tar on to rigging than study elementary ballistics. He picked up a pen with the same reluctance other men might grasp a smoking grenade.

It was curious how three clever, perceptive young men could fail to see - or, rather, to note - interesting events. A few days ago several whales were sighted, some young ones among them; last Sunday a school of dolphins played under the bow for hours like huge joyful children; on Monday seamen towing a huge hook caught a large shark and the task of killing it after it had been hoisted on board had made the decks run with blood - more blood than had ever flowed in battle. And the next day there had been a tropic bird.

For Ramage there were five things that he would always remember about the West Indies - the Tropics, in fact - even if he never visited them again: tropic birds, flying fish, blue sea, pelicans and palm trees. This tropic bird, the first of the voyage, had come up from the east, alone, passed high over the ship with a casual elegance, and flown on to the west - where the nearest land was nearly three thousand miles away. It was not a big bird but a striking one - all white with a very long forked tail. In fact the tail was three or four times longer than the bird - V-shaped like a swallow's, and very thin, as though each part comprised a single feather.

But there was no mention of whales, shark, dolphins or tropic bird in any of the journals. They were accepted like sunshine and squalls as part of a daily routine. How did one make people aware of their surroundings?

Ramage was just closing the last journal when the sentry at the door called: 'Mr Southwick, sir.'

The master came in, a cheerful grin on his sunburned face, his white hair now greasy because of the water shortage, and put a slip of paper on Ramage's desk. Usually he brought down the slate on which he had written the noon position, and the use of a piece of paper made Ramage look carefully at the figure.

The longitude was of course west of Greenwich and in the thirties, but the latitude stood out as though Southwick had written it in large figures: 9° 58' 12". The Calypso was now south of ten degrees North!

Ramage looked up at the old master and smiled. 'So we've crossed our own personal Equator! Pass the word for Mr Aitken while I find my keys. Time to break the seals!'

By the time the first lieutenant arrived in the cabin, Ramage had unlocked the drawer and taken out the packet with its four seals, each bearing the three anchors symbol of the Admiralty. It was addressed to him and bore the instructions: 'Not to be opened until south of the 10th parallel of latitude.'

It was far more exciting for Aitken and Southwick because Lord St Vincent had already told Ramage the Calypso's final destination although he had been unable to mention it to anyone else.

Ramage slid a paperknife under the seals, levered them up and opened the letter, which comprised two sheets of paper folded into three, the two ends then being folded inwards and a seal applied to each corner of the flaps. In the top right-hand corner was the usual 'By the Lords Commissioners of the Admiralty . . .' Then the elegant copperplate opened in the time-honoured way: 'I am directed by my Lords Commissioners of the Admiralty to acquaint you . . .' He continued reading to himself.