MY GRANDMOTHER remembered the potato famine in Ireland, about 1847, and she would tell me about it. The farmers weren't hit so hard, but the people came out from the cities by the thousands, and when we'd go walking on the road she would point out the places where they had died by the fences and in the ditches and in the fields....

All of us have these pictures inside our heads. We can see them, clear as scenes from a movie but silent, frozen, for some reason nearly always sunlit. We can describe them right down to who was standing where in a room, who was saying what words in that wordless dream, how the dying winter sun glinted on the bookcase. We can describe the very wallpaper.

But the picture itself, the actual scene, the sound of those lost voices, the precise soft goldness of that glint - it can never be transferred even to our closest beloved, but must remain imprisoned in our heads.

At 90 you have a lot of pictures. You tell them and write about them even though you are finally resigned, with a certain sweet despair, to the fact that you can't pass them on, not really, and that they are yours alone.

Josephine Riordan was born in County Cork, one of 10 children of a prosperous farmer. She was a nurse in World War I, serving at the great hospital near Etaples, the site of a soldier mutiny whose story was buried in a few British army memoirs until this decade. Most of her life she was a private nurse in New York, and now she lives with her daughter's family in Falls Church.

She is trying to write it all down.

"A very exciting event of my youthful school days was when the East Muskerry fox hounds chased a fox into the coppice adjoining our play yard. We watched as the dogs closed in on their prey...the men and women in their hunting-red jackets on the beautiful horses so well groomed and the dogs so sleek and shiny coated...."

Her daughter Patricia and son-in-law Eric Brestrup have built an apartment for her at one end of the comfortable suburban house. There is one grandchild, Eric, 15, still at home, and three older girls. All of them have heard the stories many times, and they encourage her to keep on with the longhand reminiscences for the next generation.

"...The turn of the century 1900 was carefully observed and cheerfully too. Every street, shop and home was illuminated. The bells of every church tolled...Our street was gaslit, and there was a ritual: As evening came, so came the old lamplighter...."

One night in 1914 when she was a student nurse at a Liverpool hospital, she took a late phone call. "Orders to mobilize have just been received," rasped the taut voice. "This is the war office. Notify your matron that she has to be ready at 6 a.m."

"I was shaking all over," she recalls. "I climbed the two flights to the matron's room and she was asleep. I nudged her awake and told her we were at war. We were both crying. We hadn't had a war in England in 60 years."

She wanted to go. Was assigned to the hospital at Etaples. Got a dark green uniform with a wide-brim hat and brass badges on the shoulders.Joined the other nurses at a beach resort hotel hear Boulogne while Etaples was completed. Finally arrived at the cold sandy forest of Etaples.

The unending stream of wounded began coming through, so many that the faces all ran together, the dying words, the names.

"That boy from Canada, Harold Barr was his name, only 17, he'd faked his age. He had a femoral wound close to the thigh artery, and he hemorrhaged profusely.... He hemorrhaged again in the afternoon and I could watch the color going out of his eyes. The light just went out of them."

He had told the nurses that his father would be coming to see him. The father had sold his business in Toronto and joined the engineers at age 60, and he came walking up the hill into Etaples just as the casket was brought down.

There are over 12,000 graves at Etaples, the largest British military cemetery in France.

The strain on the nurses was almost beyond bearing. Some Canadian nurses in the bell tent next to hers were killed in a bombing raid, their legs blown off. ("Some women wanted to die, the wish to die was very strong.") And when the planes came over every moonlit night the patients had to be moved from their cots though they begged not to. For a whole year after that, she couldn't sleep.

"I went home on leave, and the doctor said, "My dear, you're not going back, you have an exothalmic goiter and you won't be well for years." My side hurt, too. It's worse when you hold back the pain. One girl used to shout, "Oh my God," when there was an explosion, but you couldn't do that, you know, you had to keep steady."

In 1917, on the eve of Passchendaele, thousands of British soldiers mutinied against what they knew would be yet another repetition of all the other offensives planned by generals who could not seem to learn from experience.

More than that, combat veterans were simply fed up with the incredible harshness and indignities they were subjected to at the advance training camp of Etaples by officers and noncoms, many of whom had never seen a frontline trench. So they rebelled for six days, sat down on the drillground, swarmed through the camp attacking their oppressors.

Joining forces with a small army of deserters who lived in the woods outside camp, they won many concessions before subsiding. The nurses knew of the mutiny, though they didn't see it.

"We weren't allowed out in the woods, but we heard shooting and we were scared they'd come into our huts. But they had great respect for nurses."

For Josephine Riordan, it might all have been something she had imagined long ago, so thoroughly was the incident kept down for half a century.

After the war she came to New York's Bellevue Hospital and later was a private nurse at a posh sanitarium there.

"My life has been like a tapestry," she says, "things have happened that I had no power over. Coming over on the Carmania I gave seasick pills to a woman and we became friends. One night in 1921 she invited me to her place, and a man was there talking to her husband. I thought him very intelligent."

The man was James Riordan, a New Haven railroad engineer, and four years later they were married. They lived in Elmhurst, then a fashionable district of Queens, and had two children, Patricia and James, survived the Depression (she took a nursing job in Rye; he stayed home, jobless, minding the children) and another world war and a lot of good times, too.

"Then in '67 he was going out to get the paper, he'd had lunch and was coming out of the bedroom with his shirt buttoned up to go out, and he just fell on the floor. His face turned blue, and I opened his collar. It was lucky I was there."

Jim Riordan died soon after that, at 87. Seven years later she moved in with the Brestrups.

She reads the papers, watches the news, sometimes cooks a bit - she likes a serious Irish breakfast - and walks in the garden. Her daughter or a neighbor will often take her to the shopping center or to Kennedy Center for the Town Meetings she loves.

Her son-in-law, a mortgage analyst, tells her she'll live to 100 (her grandmother lived to 98, and she has two brothers in Ireland in their 80s and a sister of 78 in New York), but she prays not to.

She writes a lot of letters. "You have to write them if you want to get them." Sometimes she works on the story of her life, putting down every detail for the seven grandchildren and others not yet born.

Interesting, that bit about the Etaples mutiny. Interesting, if the book documenting it at last had never been written.

Because the idea is unbelievable on the face of it: What? British soldiers rising up against their officers? If we didn't know it was true, would we still pay attention to the sketchy recollections of Josephine Riordan? Or would we nod and smile and privately conclude the dear lady must be a bit confused? How many other hidden episodes of history lie waiting even now in the diffident memoirs of the very old? CAPTION: Picture 1, Josephine Riordan; Picture 2, Josephine Riordan in 1921