'Stop him!' Hamilton said excitedly, 'he's under an arrest!'

Todd did not move and the second lieutenant stopped after taking two steps.

Ramage heard Todd ask conversationally: 'Should I pipe hands to dinner, sir, or would you prefer that we should get under way first?'

At once Hamilton stopped, his brow wrinkled. 'Why are we hove-to?' he inquired.

'We are receiving an extra man from a frigate, sir, a seaman Smith,' Todd said, 'and we are waiting for letters.'

As the Calypso stretched southwards towards the invisible lines round the globe marking the Tropics and the Equator, Ramage was surprised to see how many ships were at sea. While tacking across the mouth of the Bay of Biscay from Ushant to the Spanish Cabo Finisterre, still marked on the British charts by the French spelling, it had been easy to guess the ports for which merchant ships had been bound.

Few made for Brest because it was primarily a naval port but several were probably heading for the mouth of the Seine with a following wind, hoping to catch the first of the flood to take them up to Honfleur and Rouen. Three outward bound had obviously left Bordeaux and were working their way out of the Bay with a steady westerly wind in several long tacks.

As the Calypso sailed down the Spanish and Portuguese coast, just in sight of the high land, they could tick off the ports simply by watching the sails of ships arriving and departing: Vigo and Oporto had been followed by an increase in numbers as they approached Lisbon and the wide but treacherous entrance to the Tagus. Many ships passed inshore as the land trended away to the eastward, curving round from Cape St Vincent to Lagos, the Rio Tinto, Cadiz, Cape Trafalgar and sharply to the Strait of Gibraltar.

'Amazing,' Southwick commented as he replaced his old but carefully preserved quadrant in its brass-cornered mahogany box. 'Half a dozen ships always in sight. In the war - surprising how long ago that seems now: all of three months, I suppose - one passed a convoy of a hundred ships, and then saw nothing for a couple of weeks. Now, the same number of ships sailing independently means you're likely to see seven a day in the Atlantic. Many more along the coasts, of course.'

For young officers like Kenton, Martin and Orsini, Ramage's deliberate tack in towards Lisbon and the Tagus had given them not only their first sight of the Portuguese capital - a view which might come in very useful in future because, as Southwick commented, one look is worth two charts - but their first look at local coasting craft.

Martin had at once compared the graceful fregatas with Thames barges, and was soon in an argument about them with Kenton and Paolo. Both types of vessel were built for the same function - to carry bulky cargoes up rivers and for short distances along the coasts. The fregatas had apple-cheeked bows and were gaily painted, often with an ancient eye painted on each side. The mast was stepped well forward but raked aft at a considerable angle like a hurricane-swept tree so that the masthead was over the cargo hatch. Nor was this a coincidence - a heavy tackle at the masthead made it easy to use the mast to hoist up the cargo, and another tackle hauled it over the side and on to the quay. The sails were loose footed and limited in size. The Thames barge, Kenton was quick to point out, was just a large box: it had none of the graceful curves of the fregata.

The practical Martin asked the obvious question: given a vessel of, say, eighty feet in length, what did you want: beauty or cargo space? It was almost impossible, he declared, to have both. With her flat bottom, straight sides, bluff bow and almost vertical stern, a Thames barge could use every possible inch for cargo. She hoisted the head of her great mainsail up the mast, and then extended the other corner with a long sprit, so that for a given length of vessel, a Thames barge could set half as much again more canvas than a fregata. And with her flat bottom, the keel in effect on the inside of the hull, she could carry a cargo up the River Crouch, the Medway, the Colne, Orwell, Yare - not to mention the Thames and the Rother and dozens of places in the Solent - and dry out to sit on the bottom when the tide left. That often meant, said Martin triumphantly, that the cargo could be unloaded directly into carts because the horses could come over the sand.

'Or get stuck in the mud,' Kenton said, waving aside Orsini's claims for the polacca of the Mediterranean. The argument was stopped when Southwick pointed out that not one of their noon sights agreed with another. 'According to Mr Kenton we must have made one great sternboard since noon yesterday. because he puts us so far north; Mr Martin would have us believe we've been making seventeen knots for the past twenty-four hours; and Mr Orsini must be teasing us.'

Gradually the latitude and longitude columns in Ramage's journal began to change radically. The longitude started off from a few minutes of arc east of Greenwich, because the Calypso had sailed from the Medway, crossing the meridian while passing westward just south of Newhaven and Rottingdean. Since then the longitude had increased as they slanted southwest while the latitude grew less. Thirty-six degrees North showed they were level with the Strait of Gibraltar; thirty-five meant they were almost as far south as Rabat and bearing away to the southwest for Madeira, having completely failed to find the northeast trades which should have hurried the Calypso down the Portuguese coast.

And at last it was getting wanner. For the time being the sun was brighter rather than hotter, but the sea was certainly not so cold and Ramage slept with the skylights propped open.

Ramage enjoyed and relived his own first voyage into the Tropics by seeing it through the eyes of Wilkins. The present voyage must be the fifth or sixth that would take him across that magic latitude, twenty-three degrees thirty-three minutes, which marked the Tropic of Cancer, the northern limit of the band circling the earth like a cummerbund and called the 'Tropics'.

Wilkins, his blond hair blowing in the trade winds, his blue eyes rarely still for a moment, was looking at the flowing waves, the sky dappled by trade wind clouds, the Calypso's sail, her deck, the movement of the men.

His first attempt to paint on deck had been disastrous: he was just settling down with brushes and palette, having drawn in with a few swift charcoal strokes the curve of the mainsail, when the combination of a lurch to leeward and a sudden puff of wind caught his canvas. The wooden frame of the stretcher hooked in his easel as it blew away and in a moment both had gone over the side, leaving a startled Wilkins still sitting on his folding stool, brush in one hand and the palette and more brushes in the other.

Ramage had run to the ship's side and seen that the easel, heavy with metal fittings, had sunk. To his surprise the seamen who had seen the accident were even more upset than Wilkins. Instead of laughing at the sight of the artist sitting on his stool apparently working on an invisible canvas, they had offered to get some more canvas from the sailmaker. Then, catching Ramage's eye and correctly interpreting the nod, the Calypso's carpenter had gone up to Wilkins and asked for a sketch of an easel with dimensions, promising a replacement by the evening in bare wood, but tomorrow evening with two coats of varnish.

While he waited for the carpenter and his mates to produce a new easel, Wilkins talked to Ramage of his plans.

'The amazing thing is,' he said, 'that in the last few days my entire world has changed. For the whole of my life the sea has been various shades of green, even though poets insist on calling it blue. The sky has been a pale blue, as weak in colour as the shell of a duck's egg.