The midnight sun shone high as Mark L. Smith, 21, a junior at the University of Texas, sat on his bunkbed with a bottle of Jack Daniels and a waterpipe. He strummed a guitar and sang a song he had composed months earlier, in the dead of the Antarctic winter night. It went like this:

Well, ya know that its been fun

But I could be home just lyin' in the sun

I could be talking with my girl

But instead I'm sittin' here bored

On the bottom of the world.

Ya know the mountains look real cool

But after a year down here I feel like a fool

And we sit here with no hope

The only way to get by is with a little dope.

Cabin fever in Antarctica is like cabin fever nowhere else. The 100 or so Americans who spend the winter here each year are cut off from the rest of the world from March to September. They watch the sun sink on the horizon until it disappears completely in April. It doesn't return until August, and even then for only a few hours a day. Temperatures dip to 100 below zero. Howling blizzards batter the buildings. People don't venture outside for weeks on end.

"Did you ever blow soap bubbles and watch them freeze?" Smith asked his friend Bob Squires, just in the night before from Siple Station, the most remote of the four U.S. scientific bases on the continent.

"Yes," Squires said. "But we ran out of soap."

When the scientists from prestigous universities and the bureaucrats from Washington leave Antarctica each February, after the bustling summer season, technicians and radio operators and mechanics remain to hold the flag aloft. The population of McMurdo, the largest base, situated on the coast, drops from 800 to 70.

So it has been for the 20 years that permanent scientific stations have operated in this bleak wilderness. Before that, only the occasional explorer braved the bone-chilling winter here either by mistake or while waiting to put together a summer expedition.

Smith, a cheerful fellow with a mop of shaggy brown hair, was one of two "winter-over" technicians to operate a satellite tracking facility here last year under a University of Texas grant. "Most of my friends thought I was crazy," he said. "But imagine having a length of time to do what you want to do as far as reading, thinking, philosophizing. You leave civilization with no strings attached."

Smith's job -- to collect data for the Defense Mapping Agency and to determine satellite positions for ships at sea -- involved two to five hours of work a day. "If nothing went wrong with the equipment, I had a lot of free time," he said.

The time wasn't always pleasant. Smith had the "big eye," as Antarctica's insomnia, a common affliction here, is known. "That was the hardest thing," he said. "And I worked the 1 a.m. to 2 p.m. shift. I didn't see a lot of people. Your sensory input is limited. You start regressing. You lose certain abilities to write and think. I wanted to write an article, but I found my vocabulary had vanished. I had trouble putting sentences together."

Navy psychiatrists who examine all winter-overs say such experiences are common. Depression strikes particularly hard during June and July when it is pitch dark around the clock. Alcoholism is a problem, and for those who have left their families at home and have no way of returning before the weather clears in October, the loneliness can be acute.

One winter-over man at Siple this year apparently thought he had a happy marriage until he learned over the ham radio that his wife was divorcing him. "If you come here often, divorce is inevitable," said one divorced geologist.

"'Drifting' is a popular pastime," Smith said. "Your eyes go out of focus. I used to spend hours sitting in the dining hall. You don't see, think, hear. It's the 'winter-over stare.'"

Squires, who was far more isolated than Smith on a base with only eight people, said he read 400 books during his nine-month stay at Siple, but he couldn't remember a single title. "It's all a blur," he said. Pressed, he remembered one: a science-fiction novel called "Earth Abides."

An electrical engineering graduate of the University of Delaware, Squires, 24, had one of the most romantic jobs in Antarctica -- watching and recording the spectacular auroras, the Southern Lights of the winter sky. Siple Station is buried under the snow but, sticking out on top, a little hut with an acrylic dome encloses a television camera with a fisheye lens pointed toward the firmament.

"It's neat," said Squires, an earnest man with a wispy beard and aviator glasses. "I'd stand up in there and tinker with the instruments and stare at the sky. Sometimes I'd walk a half mile out and lay down on the snow. The aurora starts as a band on the horizon. Then it is a green curtain stretched across the sky, kind of wavy. It always changes -- swirly reds, yellows and deep blue infrared colors. It's almost magic."

Siple is a tiny speck on a vast desert of ice, 1,500 miles from McMurdo into the wild Antarctic interior. "I bet you have never seen a perfectly flat horizon," Squires said. Underground, the station's total living space is 150 feet by 30 feet. Squires' room, decorated with a Sierra Club calendar and two Penthouse pinups, was "very homey," he said.

"You could sit in your room and tell by the footsteps who was walking by. . . . Sometimes I didn't see people for a week. The news from the real world would come over the teletype machine, but I stopped reading it after a few months. I didn't know Mount St. Helens had blown up."

Once a month, Squires could use a retired satellite to talk to his parents or girlfriend. Once a week, Siple would radio Vostok, a Soviet station across the continent, to give the next move in a chess game, which, by the end of the season, the Russians won.

"You float," Squires said. "You never know what time of day it is. When you're tired you go to bed. When you're rested, you wake up. You don't know whether to eat breakfast or dinner. You're on your own. You work for an hour. You read for an hour. Then you go back to work."

Flying into McMurdo from the lifeless interior, Squires said, he had been suddenly frightened by the sight of a bird. "I hadn't seen one single living thing in a year. We'd kept a bug in a jar and fed it frozen vegetables. When it died we pinned it up on the bar."

Not everyone can survive such a life. Isolation can bring out unpredictable hostility and insecurity. At Siple one year, Squires said, a group played a joke on a man prone to superstition by painting footprints on the snow with chicken blood and surrounding them with torn clothing. They then reported the disappearance of one of the residents. When the man found the footprints, he became acutely paranoid, believed he was going to be killed, and ended up camping out alone in an abandoned building for a month.

The National Science Foundation, which runs the bases, is not anxious to publicize such incidents, but officials acknowledge that some unbalanced people manage to slip through the psychological testing required for winter-overs. One man who had come to spend the winter began, after a few weeks, to say he was the reincarnation of Galileo, and was quickly shipped out, according to an NSF official.

Compared to Siple and South Pole stations, McMurdo is a big city. In the summer, four bars serve liquor, to the blare of rock music. The little Chapel of the Snows, in a canvas-covered Jamesway hut, conducts regular Sunday services. The fire station features a paneled Jacuzzi bath. The mess hall offers mushroom and cheese omelets made to order, fresh kiwi fruit flown in from New Zealand and pina colada-flavored frozen yogurt.

Residents limit themselves to one shower a week to avoid wasting fuel needed to operate the water desalinization plant. But energy is squandered in the dormitories, where the constant 85-degree heat forces people to keep windows open despite freezing temperatures outside. The new power plant here has only 2 1/2 inches of insulation, half that used at a nearby New Zealand base. oAt McMurdo's dump, New Zealanders stock up on machinery, lumber and even frozen beer that the Americans have thrown away.

In the winter, McMurdo is quiet, but Smith had good times playing his guitar, learning Russian cusswords and drinking vodka with a Soviet geologist on exchange here, and occasionally taking moonlit walks by the frozen sea. Video cassette television offered "Mash," the Muppets, "Dallas" and other popular programs. As for movies, Smith said, "I saw 'Smokey and the Bandit' three dozen times."

And, of course, there was local gossip to worry about: the radio waves from the South Pole were burning with the news that a mystery man had clipped all the marijuana plants so carefully cultivated under lights. And at McMurdo, two born-again Christians, Navy enlisted men, threatened to tell their superiors about the regular skinflicks. They were dissuaded by "peer pressure," Smith said.

Women are still a controversial subject in Antarctica. Women scientists did not even visit the South Pole until 1969, more than 10 years after the United States established a permanent base. For the last three years, a single woman and 16 men have wintered at the Pole, creating tensions, according to some old hands who would rather not see females here at all.

"I wasn't prepared to find women in the Antarctic," said John Annextad, a veteran polar scientist. "I'm used to going to a celibate society. You come here prepared to live without sex.All of a sudden the world is changing."

Among winter-overs, "sex becomes an obsession," said Noah White, a communications expert who has spent three winters in Antarctica. "I've had two psychologists tell me that one's sex drive diminishes greatly during a winter here. That's bulls??t." White calls the abundance of skinflicks "memory aide movies -- so we know what to do when we go back home."

For the last two years, memories were partly aided by radio broadcasts from a Georgetown University station. Jorge Carnicero, 28, an amateur radio operator who worked at the Riggs National Bank during the day and at the station at night, said he would talk to the South Pole every evening. Besides reading the sports pages to his airwave pals, he would recruit groups of Georgetown nurses to compete for "the sexiest voice in the Antarctic."

"These guys would go wild talking to a female," said Carnicero, who is working here as a radio operator this summer. "And the nurses got a kick out of talking to the South Pole. They'd become totally uninhibited -- especially one who called herself 'Robin, the oral specialist.' Everything had a double meaning."

From a woman's perspective, however, Antarctica "is like being a bone in a pack of dogs," said Julia Uberuaga, a summer South Pole resident. In summer, there are three women and 65 men at the Pole, 50 and 800 at McMurdo.

Whatever the hardships for both sexes, psychologists report that 90 percent of those interviewed after their antarctic stay describe it as the most satisfying experience of their lives. "I don't regret a minute of it," said Mark Smith, the satellite technician. Bob squires said he came for "the adventure, to do something different. Now I don't think I'll ever get back into the 9-to-5 rut again."