THE NAUTILUS didn't change direction. For the time being, then, we had to set aside any hope of returning to European seas. Captain Nemo kept his prow pointing south. Where was he taking us? I was afraid to guess.

That day the Nautilus crossed an odd part of the Atlantic Ocean. No one is unaware of the existence of that great warm-water current known by name as the Gulf Stream. After emerging from channels off Florida, it heads toward Spitzbergen. But before entering the Gulf of Mexico near latitude 44 degrees north, this current divides into two arms; its chief arm makes for the shores of Ireland and Norway while the second flexes southward at the level of the Azores; then it hits the coast of Africa, sweeps in a long oval, and returns to the Caribbean Sea.

Now then, this second arm--more accurately, a collar--forms a ring of warm water around a section of cool, tranquil, motionless ocean called the Sargasso Sea. This is an actual lake in the open Atlantic, and the great current's waters take at least three years to circle it.

Properly speaking, the Sargasso Sea covers every submerged part of Atlantis. Certain authors have even held that the many weeds strewn over this sea were torn loose from the prairies of that ancient continent. But it's more likely that these grasses, algae, and fucus plants were carried off from the beaches of Europe and America, then taken as far as this zone by the Gulf Stream. This is one of the reasons why Christopher Columbus assumed the existence of a New World. When the ships of that bold investigator arrived in the Sargasso Sea, they had great difficulty navigating in the midst of these weeds, which, much to their crews' dismay, slowed them down to a halt; and they wasted three long weeks crossing this sector.

Such was the region our Nautilus was visiting just then: a genuine prairie, a tightly woven carpet of algae, gulfweed, and bladder wrack so dense and compact a craft's stempost couldn't tear through it without difficulty. Accordingly, not wanting to entangle his propeller in this weed-choked mass, Captain Nemo stayed at a depth some meters below the surface of the waves.

The name Sargasso comes from the Spanish word "sargazo," meaning gulfweed. This gulfweed, the swimming gulfweed or berry carrier, is the chief substance making up this immense shoal. And here's why these water plants collect in this placid Atlantic basin, according to the expert on the subject, Commander Maury, author of The Physical Geography of the Sea.

The explanation he gives seems to entail a set of conditions that everybody knows: "Now," Maury says, "if bits of cork or chaff, or any floating substance, be put into a basin, and a circular motion be given to the water, all the light substances will be found crowding together near the center of the pool, where there is the least motion. Just such a basin is the Atlantic Ocean to the Gulf Stream, and the Sargasso Sea is the center of the whirl."

I share Maury's view, and I was able to study the phenomenon in this exclusive setting where ships rarely go. Above us, huddled among the brown weeds, there floated objects originating from all over: tree trunks ripped from the Rocky Mountains or the Andes and sent floating down the Amazon or the Mississippi, numerous pieces of wreckage, remnants of keels or undersides, bulwarks staved in and so weighed down with seashells and barnacles, they couldn't rise to the surface of the ocean. And the passing years will someday bear out Maury's other view that by collecting in this way over the centuries, these substances will be turned to stone by the action of the waters and will then form inexhaustible coalfields. Valuable reserves prepared by farseeing nature for that time when man will have exhausted his mines on the continents.

In the midst of this hopelessly tangled fabric of weeds and fucus plants, I noted some delightful pink-colored, star-shaped alcyon coral, sea anemone trailing the long tresses of their tentacles, some green, red, and blue jellyfish, and especially those big rhizostome jellyfish that Cuvier described, whose bluish parasols are trimmed with violet festoons.

We spent the whole day of February 22 in the Sargasso Sea, where fish that dote on marine plants and crustaceans find plenty to eat. The next day the ocean resumed its usual appearance.

From this moment on, for nineteen days from February 23 to March 12, the Nautilus stayed in the middle of the Atlantic, hustling us along at a constant speed of 100 leagues every twenty-four hours. It was obvious that Captain Nemo wanted to carry out his underwater program, and I had no doubt that he intended, after doubling Cape Horn, to return to the Pacific South Seas.

So Ned Land had good reason to worry. In these wide seas empty of islands, it was no longer feasible to jump ship. Nor did we have any way to counter Captain Nemo's whims. We had no choice but to acquiesce; but if we couldn't attain our end through force or cunning, I liked to think we might achieve it through persuasion. Once this voyage was over, might not Captain Nemo consent to set us free in return for our promise never to reveal his existence? Our word of honor, which we sincerely would have kept. However, this delicate question would have to be negotiated with the captain. But how would he receive our demands for freedom? At the very outset and in no uncertain terms, hadn't he declared that the secret of his life required that we be permanently imprisoned on board the Nautilus? Wouldn't he see my four-month silence as a tacit acceptance of this situation? Would my returning to this subject arouse suspicions that could jeopardize our escape plans, if we had promising circumstances for trying again later on? I weighed all these considerations, turned them over in my mind, submitted them to Conseil, but he was as baffled as I was. In short, although I'm not easily discouraged, I realized that my chances of ever seeing my fellow men again were shrinking by the day, especially at a time when Captain Nemo was recklessly racing toward the south Atlantic!

During those nineteen days just mentioned, no unique incidents distinguished our voyage. I saw little of the captain. He was at work. In the library I often found books he had left open, especially books on natural history. He had thumbed through my work on the great ocean depths, and the margins were covered with his notes, which sometimes contradicted my theories and formulations. But the captain remained content with this method of refining my work, and he rarely discussed it with me. Sometimes I heard melancholy sounds reverberating from the organ, which he played very expressively, but only at night in the midst of the most secretive darkness, while the Nautilus slumbered in the wilderness of the ocean.

During this part of our voyage, we navigated on the surface of the waves for entire days. The sea was nearly deserted. A few sailing ships, laden for the East Indies, were heading toward the Cape of Good Hope. One day we were chased by the longboats of a whaling vessel, which undoubtedly viewed us as some enormous baleen whale of great value. But Captain Nemo didn't want these gallant gentlemen wasting their time and energy, so he ended the hunt by diving beneath the waters. This incident seemed to fascinate Ned Land intensely. I'm sure the Canadian was sorry that these fishermen couldn't harpoon our sheet-iron cetacean and mortally wound it.

During this period the fish Conseil and I observed differed little from those we had already studied in other latitudes. Chief among them were specimens of that dreadful cartilaginous genus that's divided into three subgenera numbering at least thirty-two species: striped sharks five meters long, the head squat and wider than the body, the caudal fin curved, the back with seven big, black, parallel lines running lengthwise; then perlon sharks, ash gray, pierced with seven gill openings, furnished with a single dorsal fin placed almost exactly in the middle of the body.

Some big dogfish also passed by, a voracious species of shark if there ever was one. With some justice, fishermen's yarns aren't to be trusted, but here's what a few of them relate. Inside the corpse of one of these animals there were found a buffalo head and a whole calf; in another, two tuna and a sailor in uniform; in yet another, a soldier with his saber; in another, finally, a horse with its rider. In candor, none of these sounds like divinely inspired truth. But the fact remains that not a single dogfish let itself get caught in the Nautilus's nets, so I can't vouch for their voracity.

Schools of elegant, playful dolphin swam alongside for entire days. They went in groups of five or six, hunting in packs like wolves over the countryside; moreover, they're just as voracious as dogfish, if I can believe a certain Copenhagen professor who says that from one dolphin's stomach, he removed thirteen porpoises and fifteen seals. True, it was a killer whale, belonging to the biggest known species, whose length sometimes exceeds twenty-four feet. The family Delphinia numbers ten genera, and the dolphins I saw were akin to the genus Delphinorhynchus, remarkable for an extremely narrow muzzle four times as long as the cranium. Measuring three meters, their bodies were black on top, underneath a pinkish white strewn with small, very scattered spots.

From these seas I'll also mention some unusual specimens of croakers, fish from the order Acanthopterygia, family Scienidea. Some authors-- more artistic than scientific--claim that these fish are melodious singers, that their voices in unison put on concerts unmatched by human choristers. I don't say nay, but to my regret these croakers didn't serenade us as we passed.

Finally, to conclude, Conseil classified a large number of flying fish. Nothing could have made a more unusual sight than the marvelous timing with which dolphins hunt these fish. Whatever the range of its flight, however evasive its trajectory (even up and over the Nautilus), the hapless flying fish always found a dolphin to welcome it with open mouth. These were either flying gurnards or kitelike sea robins, whose lips glowed in the dark, at night scrawling fiery streaks in the air before plunging into the murky waters like so many shooting stars.

Our navigating continued under these conditions until March 13. That day the Nautilus was put to work in some depth-sounding experiments that fascinated me deeply.

By then we had fared nearly 13,000 leagues from our starting point in the Pacific high seas. Our position fix placed us in latitude 45 degrees 37' south and longitude 37 degrees 53' west. These were the same waterways where Captain Denham, aboard the Herald, payed out 14,000 meters of sounding line without finding bottom. It was here too that Lieutenant Parker, aboard the American frigate Congress, was unable to reach the underwater soil at 15,149 meters.

Captain Nemo decided to take his Nautilus down to the lowest depths in order to double-check these different soundings. I got ready to record the results of this experiment. The panels in the lounge opened, and maneuvers began for reaching those strata so prodigiously far removed.

It was apparently considered out of the question to dive by filling the ballast tanks. Perhaps they wouldn't sufficiently increase the Nautilus's specific gravity. Moreover, in order to come back up, it would be necessary to expel the excess water, and our pumps might not have been strong enough to overcome the outside pressure.

Captain Nemo decided to make for the ocean floor by submerging on an appropriately gradual diagonal with the help of his side fins, which were set at a 45 degrees angle to the Nautilus's waterline. Then the propeller was brought to its maximum speed, and its four blades churned the waves with indescribable violence.

Under this powerful thrust the Nautilus's hull quivered like a resonating chord, and the ship sank steadily under the waters. Stationed in the lounge, the captain and I watched the needle swerving swiftly over the pressure gauge. Soon we had gone below the livable zone where most fish reside. Some of these animals can thrive only at the surface of seas or rivers, but a minority can dwell at fairly great depths. Among the latter I observed a species of dogfish called the cow shark that's equipped with six respiratory slits, the telescope fish with its enormous eyes, the armored gurnard with gray thoracic fins plus black pectoral fins and a breastplate protected by pale red slabs of bone, then finally the grenadier, living at a depth of 1,200 meters, by that point tolerating a pressure of 120 atmospheres.

I asked Captain Nemo if he had observed any fish at more considerable depths.

"Fish? Rarely!" he answered me. "But given the current state of marine science, who are we to presume, what do we really know of these depths?"

"Just this, captain. In going toward the ocean's lower strata, we know that vegetable life disappears more quickly than animal life. We know that moving creatures can still be encountered where water plants no longer grow. We know that oysters and pilgrim scallops live in 2,000 meters of water, and that Admiral McClintock, England's hero of the polar seas, pulled in a live sea star from a depth of 2,500 meters. We know that the crew of the Royal Navy's Bulldog fished up a starfish from 2,620 fathoms, hence from a depth of more than one vertical league. Would you still say, Captain Nemo, that we really know nothing?"

"No, professor," the captain replied, "I wouldn't be so discourteous. Yet I'll ask you to explain how these creatures can live at such depths?"

"I explain it on two grounds," I replied. "In the first place, because vertical currents, which are caused by differences in the water's salinity and density, can produce enough motion to sustain the rudimentary lifestyles of sea lilies and starfish."

"True," the captain put in.

"In the second place, because oxygen is the basis of life, and we know that the amount of oxygen dissolved in salt water increases rather than decreases with depth, that the pressure in these lower strata helps to concentrate their oxygen content."

"Oho! We know that, do we?" Captain Nemo replied in a tone of mild surprise. "Well, professor, we have good reason to know it because it's the truth. I might add, in fact, that the air bladders of fish contain more nitrogen than oxygen when these animals are caught at the surface of the water, and conversely, more oxygen than nitrogen when they're pulled up from the lower depths. Which bears out your formulation. But let's continue our observations."

My eyes flew back to the pressure gauge. The instrument indicated a depth of 6,000 meters. Our submergence had been going on for an hour. The Nautilus slid downward on its slanting fins, still sinking. These deserted waters were wonderfully clear, with a transparency impossible to convey. An hour later we were at 13,000 meters-- about three and a quarter vertical leagues--and the ocean floor was nowhere in sight.

However, at 14,000 meters I saw blackish peaks rising in the midst of the waters. But these summits could have belonged to mountains as high or even higher than the Himalayas or Mt. Blanc, and the extent of these depths remained incalculable.

Despite the powerful pressures it was undergoing, the Nautilus sank still deeper. I could feel its sheet-iron plates trembling down to their riveted joins; metal bars arched; bulkheads groaned; the lounge windows seemed to be warping inward under the water's pressure. And this whole sturdy mechanism would surely have given way, if, as its captain had said, it weren't capable of resisting like a solid block.

While grazing these rocky slopes lost under the waters, I still spotted some seashells, tube worms, lively annelid worms from the genus Spirorbis, and certain starfish specimens.

But soon these last representatives of animal life vanished, and three vertical leagues down, the Nautilus passed below the limits of underwater existence just as an air balloon rises above the breathable zones in the sky. We reached a depth of 16,000 meters-- four vertical leagues--and by then the Nautilus's plating was tolerating a pressure of 1,600 atmospheres, in other words, 1,600 kilograms per each square centimeter on its surface!

"What an experience!" I exclaimed. "Traveling these deep regions where no man has ever ventured before! Look, captain! Look at these magnificent rocks, these uninhabited caves, these last global haunts where life is no longer possible! What unheard-of scenery, and why are we reduced to preserving it only as a memory?"

"Would you like," Captain Nemo asked me, "to bring back more than just a memory?"

"What do you mean?"

"I mean that nothing could be easier than taking a photograph of this underwater region!"

Before I had time to express the surprise this new proposition caused me, a camera was carried into the lounge at Captain Nemo's request. The liquid setting, electrically lit, unfolded with perfect clarity through the wide-open panels. No shadows, no blurs, thanks to our artificial light. Not even sunshine could have been better for our purposes. With the thrust of its propeller curbed by the slant of its fins, the Nautilus stood still. The camera was aimed at the scenery on the ocean floor, and in a few seconds we had a perfect negative.

I attach a print of the positive. In it you can view these primordial rocks that have never seen the light of day, this nether granite that forms the powerful foundation of our globe, the deep caves cut into the stony mass, the outlines of incomparable distinctness whose far edges stand out in black as if from the brush of certain Flemish painters. In the distance is a mountainous horizon, a wondrously undulating line that makes up the background of this landscape. The general effect of these smooth rocks is indescribable: black, polished, without moss or other blemish, carved into strange shapes, sitting firmly on a carpet of sand that sparkled beneath our streams of electric light.

Meanwhile, his photographic operations over, Captain Nemo told me:

"Let's go back up, professor. We mustn't push our luck and expose the Nautilus too long to these pressures."

"Let's go back up!" I replied.

"Hold on tight."

Before I had time to realize why the captain made this recommendation, I was hurled to the carpet.

Its fins set vertically, its propeller thrown in gear at the captain's signal, the Nautilus rose with lightning speed, shooting upward like an air balloon into the sky. Vibrating resonantly, it knifed through the watery mass. Not a single detail was visible. In four minutes it had cleared the four vertical leagues separating it from the surface of the ocean, and after emerging like a flying fish, it fell back into the sea, making the waves leap to prodigious heights.