'Ply the oar, ma'am?' said Jack, looking up from his paper, his pen poised.

'Is it not right? I was so proud of it.'

'Oh yes,' said Jack. 'Only the word is spelt rather odd, you know,' and he wrote she would not play the whore very carefully, so that the letters could not be mistaken, smiling secretly as he did so, his frustration and disappointment entirely overcome by his sense of the ridiculous.

They parted on excellent terms, and she gave him a particularly friendly look as she said 'You will not forget my party, will you? I have Count Muratori coming, with his lovely flute.'

'Nothing shall keep me away,' said Jack, 'short of the loss of both legs. And even then there is always a stretcher.'

'And you will remember it to the Doctor?' she said.

'He will remember it to himself, I am sure,' said Jack, holding the door open for her. 'And if he don't . . . but there he is,' he said, cocking his ear to the stairs. 'He often comes up more like a herd of mad sheep than a Christian, when he is in a hurry.'

Dr Maturin it was, and his face, ordinarily pale, grave, and withdrawn, shone pink with haste and happiness. 'Why, you are all wet,' they both cried; and indeed a little pool was fast gathering at his feet as he stood there before them. Jack was on the point of asking 'Did you fall in?', but he did not like to expose his friend, since the answer must necessarily be yes: Dr Maturin was wonderfully unhandy at sea, and very often, in clambering from boat to ship or even in stepping from a solid, stone-built quay into a motionless dghaisa, a local craft expressly designed for the safe, dry transport of landlubbers, he would contrive to miss his footing and plunge into the sea - so much so that his smallclothes and the skirts of his coat ordinarily showed whitish tide-marks, where the salt had dried.

Laura Fielding had no such inhibitions however and her 'Did you fall in?' came out as naturally as the day.

'Your most devoted, ma'am,' said Stephen, absent-mindedly kissing her hand. 'Jack, give me joy. The Dromedary is come in!'

'What of it?' said Jack, who had seen the slab-sided transport beating up, tack upon tack, since early dawn.

'She has my diving-bell aboard!'

'What diving-bell?'

'My long-awaited Halley's diving-bell. I had almost lost hope of it, so I had. It has a window in the top! I am with child to plunge. You must come and see it at once - I have a dghaisa at the waterside.'

'Gentlemen, good day,' said Mrs Fielding, who was not accustomed to being slighted for a diving-bell.

They begged her pardon. They were extremely sorry: they had meant no disrespect, and Stephen handed her down the stairs with Jack and Ponto following solemnly.

'It is Halley's model, you know,' said Stephen as the long, lean dghaisa shoved off and began to skim across the Grand Harbour towards the Dromedary, urged by the promise of double fare. 'How briskly these worthy creatures do propel the bark, to be sure; and have you noticed that they stand up to do so, that they face the direction they are going, like the gondoliers of Venice? Surely this is a laudable practice that should be introduced into the Navy.'

Stephen often put forward ideas for the improvement of the service. In his time he had advocated the serving out of a modest allowance of soap, the cutting of the monstrous rum-ration, the provision of free, warm, serviceable uniform clothes for the lower deck, particularly for the ship's boys and new hands, and the abolition of such punishments as flogging round the fleet: these proposals had met with little more success than his present suggestion that in defiance of all tradition the Navy should look where it was going - Jack swept straight past it, saying eagerly 'Halley? Comet Halley, the Astronomer Royal?'

'Just so.'

'I knew he commanded the Paramour pink, when he was working on the southern stars and the Atlantic chart,' said Jack, 'and I have an amazing respect for him, of course. Such an observer! Such a calculator! But I had no idea he was concerned with diving-bells.'

'Yet I told you of his paper, the Art of Living under Water, in the Philosophical Transactions, and you commended my desire to walk upon the bottom of the sea. You said it would be a better way of finding lost anchors and cables than creeping for them with a grapnel.'

'I remember it perfectly. But you did not mention Dr Halley's name, and you spoke of some kind of a helmet with tubes, no more.'

'I certainly mentioned Dr Halley's name, so I did, and I treated the bell at some length; but you did not attend.

You were playing cricket at the time: you were watching out, and I came and stood by you.'

'That was on another occasion, when we were playing the gentlemen of Hampshire: I had to desire Babbington to lead you away. I have never been able to make you understand how seriously we take the game in England. However, pray tell me again. What is the principle of the bell?'

'It is beautiful in its simplicity! Imagine a truncated cone, open at the bottom, furnished with a stout glass window at the top, and so weighted that on being lowered into the sea it sinks perpendicularly; a commodious bell whose occupant sits at his ease upon a bench diametrically placed a little above the lower rim, enjoying the light that shines upon him from the glass above, and revelling in the wonders of the deep. You will object that as the bell sinks, the air within becomes compressed and the water rises proportionably,' said Stephen, holding up his hand, 'and in ordinary circumstances this is profoundly true, so that at thirty-three feet the bell would be half full. But you are also to imagine a barrel, similarly weighted and provided with a hole at the bottom and another at the top. The top hole has a leathern hose fitted to it, an air-tight, water-tight leathern hose, well dressed with oil and beeswax, while the bottom hole is open, to let the sea in as the barrel sinks.'

'What is the good of that?'

'Why, do you not see? It replenishes the bell with air.'

'Not at all. The air has rushed out by way of your leathern hose.'

The remark struck Stephen dumb. He opened his mouth, then closed it; and for some minutes, as the slim boat ran fast through the ships and small craft in the Grand Harbour, with the noble mass of the Three Cities ahead and Valletta astern, the air itself blue from the high and brilliant sky, he puzzled over the problem. Then his face cleared; the delight came back, and he cried, 'Why, of course, of course: what a brute-beast I am! I had quite forgot to say that the leathern hose is kept below the lower bung-hole by an appended weight. It is kept down during the barrel's descent - that is of the essence - and the man inside the bell grasps it, pulls it in, and raises it. As soon as he has raised it above the surface of the water in the barrel, the confined air rushes into the bell with great force, refreshing him and repelling the sea in the lower part of the machine. He then gives a signal, and as the first barrel is hauled up, so another comes down. Dr Halley says - and these, Jack, are his very words -"an alternate succession furnished air so quick, and in so great plenty, that I have myself been one of five who have been together at the bottom, in nine or ten fathom water, for above an hour and a half at a time, without any ill effects."

'Five people!' cried Jack. 'God love me, it must be a most enormous affair. Pray what are its dimensions?'

'Oh,' said Stephen, 'mine is only a modest bell, a small little bell indeed. I doubt you could get into it.'

'What does it weigh?'

'Sure, I forget the exact figure; but very little at all -only just enough to make it sink, and sink slowly at that.

Will you look at that bird, almost directly ahead, at some thirty-five degrees of elevation? I believe it to be a hangi. They are said to be peculiar to this island.'