THE YEAR is 1903. A 13-year-old boy in a little English town has started keeping a journal. At first it's practically all science. "Am writing an essay on the life-history of insects, and have abandoned the idea of writing on 'How Cats Spend Their Times,'" he notes. Later he takes a sort of vow to learn all about beetles.

The boy's name is Bruce Cummings, and he comes from a background as drab as his name. His father works for an obscure provincial newspaper, making just enough money to count as middle class. Nobody in that family goes to college. Everybody in its start work young.

Bruce picked the wrong family to be born in. What he wants is education -- lots of it, at the best schools -- and then fame. He'd like to be a great biologist, preferably the greatest of his generation.

He knows he has the temperament. By the time he's 15, he is reading Darwin, dissecting leeches, teaching himself chemistry. At 16, when he catches measles, he can look at his own body with a clam scientific eye and note "I have somewhere near 10,000 spots on me." He can look at his mind (he loves to do this -- he is self-intoxicated) and suspect himself of genious. And all the time he is pouring thoughts into his journal. What he doesn't know yet is that he is an extraordinarily good writer.

But the English class system does not easily let go of people. Seventy-five years ago, it hardly let go at all.

At barely, 17, Bruce Cummings left school forever, and reluctantly signed what he called his Death Warrant -- a 5-year bond of apprenticeship on his father's paper. Being stubborn, he continued studying biology, physics, chemistry and German in the evenings, and dissecting owls and frogs on Sundays. But he was trapped.

There was one escape route. The British government supported a tiny handful of research institutions. Staff jobs in them were filled by competitive examination. Win the exam, and you got the job. Unfortunately for poor boys, such exams were not open to just anybody; you had to be invited to take them. Ordinarily, smart young graduates of Oxford, Cambridge, and London got invited, having been nominated by their professors. But if a Devonshire apprentice could get nominated, he did have a right to sit the exam, too.

The year he turned 21, Cummings managed to get a nomination. Three places were open in the British Museum of Natural History. He did pretty well for someone with no academic training -- he came in fourth.

The next year he did even better. There was another competition, this time for two jobs. He placed first by a wide margin. And so at 22 he vaulted up in the social structure, moved to London, and became a scientist. "I'm in, in in!" he writes in his journal.

Soon his keen provincial eye is noting all the wonders of London. He begins to publish in magazines. He discovers Beethoven, and goes in ectasy to hear Sir Henry Wood conduct the Fifth. He drops his drab provincial name, and flames out as W.N.P. Barbellion. (The whole name is charged with significance, Besides its pleasing foreignness, Barbellion combines "barbarian" and "rebellion." As for three initials, they were and still are a class indicator in England -- they indicate gentry. The three names Barbellion hid behind those chaste initials indicate . . . well, you'll see later.)

This is a delightful success story, made still more delightful by the fact that Barbellion was such a lively man. Many scientists are brilliant, single-focuses, and boring. Barbellion was brilliant, multi-focused, and fascinating. From age 16 on, his journal gradually expanded to include all the things that interested him.

For example, there were girls. Barbellion adored girls, both in the reverent Victorian fashion, and in every other fashion you can think of. He even adored them scientifically. Once in Devonshire he spent an evening with a girl named Mary. Afterwards he wrote in his journal, "I hope to goodness she doesn't think I want to marry her. In the Park in the dark, kissing her. I was testing and experimenting with a new experience."

In London, he sits behind an Irish girl (and her date) in a theater. "She was dark, with shining blue eyes, and a delightful little nose of the utmost import to every male who should gaze upon her." They manage to exchange smiles -- and all night he can think of nothing else. Two days later a newspaper is indignantly refusing to run his ad trying to get in touch with her, they suspect he's recruiting prostitutes.

When he gets engaged, age 25, to a young woman artist he truly reveres he can be surprised to find that in the middle of what he calls a "devotional" embrace, a part of his mind is thinking, "Hot stuff, this witch." Few minds allowed such thoughts to surface then, much less directed their bodies to rush home and record them.

If Barbellion had lived to be a Fellow of the Royal Society, an old professor with a knighthood, as he dreamed of doing, his journal would still be among the 20 or so best in English. But he didn't live. His knowledge that he wouldn't is what gives the journal its greatest poignancy. I have saved one aspect of his story until now.

Back when he was 20, still in Devonshire, he got handed a second death warrant -- and this one was no metaphor for a disagreeable job, but a warrant in earnest. He had a terrifying heart attack, and the doctor who treated him discovered he'd been born with an incurable disease. He could count on dying young. He could also count on lots more attacks, and eventually on being bedridden.

From then until he actually did die, just after his 30th birthday, Barbellion lived with redoubled intensity. Another man might have gone into depression, especially as the partial paralysis began. Certainly Barbellion had his dark hours. It is in the sense that this is the journal of a disappointed man.

But being who he was, he mostly responded by trying to cram 50 years of life into one little decade, half of which he was sick. To an astonishing extent he succeeded. This journal is one of the great affirmations in our literature. If I had a friend who found life tedious, who was maybe even suicidal, and I had the power to make him or her read one book, it would be the soul-stirring diary of Wilhelm Nero Pilate Barbellion. Alias Bruce Cummings.