THE DIARY OF BEATRICE WEBB; Volume Four, 1924-1943, "The Wheel of Life". Edited by Norman and Jeanne MacKenzie. Belknap/Harvard University Pr ess. 519 pp. $25.

WE ARE NOT ourselves spectacular," Beatrice Webb confessed, in her seventies, of herself and her husband, Sidney; "We have always lived in the shadows among the dry- as-dusts. . . . " The fourth and final volume of extracts from her diaries, often exasperating, sometimes moving, never humorous but always illuminating, chronicles their lives in the shadows of the between-the-wars years. Not even the short-lived Labor government of 1924, in which Sidney Webb became Lord Passfield in order to take a seat in the cabinet -- colonial secretary in the very office where he had begun his career as a clerk -- lifted Beatrice's chronic depression. She even refused to be addressed as Lady Passfield. It was too late in life, and her means were too slender, to make such a fuss. Besides, she knew the government would fail.

Failed dreams satisfied Beatrice Webb as much as did success. The frustrated mystic in her was always at odds with her sociologist and ideologue side, and while the inner light flickered, the light that really failed her at the end, however she tried to lie to herself, was the Red Star of Stalinism. The note of regret is constant. Reading through her diaries to write an early autobiography, she wondered "whether all our personal work (coupled with intrigue) to get this reform or that carried into law, to convert this group or that . . . to our way of thinking, was worthwhile from the standpoint of the community?" Judged by the deteriorating condition of Britain in the middle 1930s, she thought -- and her lines have bleak relevance today as well -- "it looks as if we socialist refmers failed to stop the rot, as if our self-complacency was unwarranted."

The manuscript diaries, archived at the London School of Economics and Political Science, which the Webbs founded, are filled with political and social gossip, brilliant capsule biographies, poignant personal narrative and flashes of events in which the Webbs were a behind-the-scenes force. They are a mine for historians seeking the texture of life in England from the 1870s into the wartime 1940s. More than anything else, however, they become the log of Beatrice Webb's spiritual odyssey. Old age, Charles de Gaulle once said, is a shipwreck. At the close, with Beatrice dying, and Sidney vegetating in the half-life aftermath of a stroke, it is not only a thwarted personal voyage that the diaries represent, but the wreckage of the Marxist dream that had propelled the Webbs and their contemporaries into politics before the tantalizing doctrines had been put to the test. It is one thing to die full of zeal for the romantic cause; it is another to live into shattered old age and see the ideal as apparently incapable of application, because human beings, individually and in the mass, remain stubbornly unsaintly.

The first Labor cabinet exposed a collection of impractical ideologues and vain social climbers. Beatrice was glad she had distanced herself from its embarrassments. When Labor had its next opportunity, in 1929, and Ramsay Macdonald -- who looked as much a prime minister as Warren Harding did a president -- sold out his colleagues (including Sidney) in order to cling to office in a coalition ministry far more Tory than Labor, Beatrice still saw the seductive socialist future as possible, if more remote. "When and where shall we find a leader who will be fervent in faith, scientific in method and really equalitarian in manners and aims? Perhaps he was killed in the Great War?" There was pathos in the concept, for a generation of British leadership had been decimated in Flanders. But, except for brief and unhappy moments in history, politics has never been the occupation of saints and martyrs.

In the 1930s Beatrice would find the hope of the world in the unlikely person of Stalin. From a distance, she perceived a "despotically controlled Communism," but attributed that to "fanatic fervour." Then she and Sidney visited Russia, and while realizing the existence of "a dark side, which we personally had little opportunity of observing," including "the repression of heresy," they succumbed to the need to believe. Their first edition of Soviet Communism. A New Civilization? was followed by a second which dropped the question mark.

With Depression in America suggesting the limits of unbridled capitalism, and the rise of Hitler foreshadowing a grim future for Europe, the Webbs congratulated themselves as the last of the late-Victorian Socialists to remain incorruptibly visionary. Their old friends Bernard and Charlotte Shaw were enjoying fame andwealth. Although Charlotte was the chief living benefactor of the L.S.E. and her hugely successful husband continued to call himself by the old radical labels, Beatrice insisted that "the Shaws neither like nor believe in the proletariat and its leaders: they live . . . among the ennobled and enlightened plutocrats." Beatrice despised Shaw's mordant political farces which satirized the ineptitude of democratic institutions, yet her diary, naming names, confirmed many of Shaw's views, and it was painful to have to accept for him, when recovering from kidney surgery, a gift of a crucial thousand pounds. Satirizing government appeared more rewarding than studying it.

After yet another play mocking at ineffectual democracies, Beatrice asked Shaw bluntly why he admired the current crop of dictators and dictator-aspirants. They had no principles, G.B.S. quipped, but they had personality. They "secured the obedience and devotion of their people," while British politicians were "self-complacent" and "spineless." It was not Shaw's finest hour, nor was it Britain's. In forceful leadership he saw cures to the weaknesses of parliamentary democracy for which the Webbs grasped at Moscow.

OLD RADICALS of every persuasion had difficulty swallowing Stalin's purge trials and then his pact with Hitler. Even before the enormity of the non-aggression pact, Beatrice was writing, dejectedly, with European war imminent, "How long shall we linger on the stage and watch horror we cannot prevent? One of the painful thoughts of old age is that one is a parasite, no longer worth keeping alive." As the war began in 1939, the Webbs clung to Russia because their lives otherwise would have seemed empty of meaning. Fortunately, when Hitler turned on Stalin two years later, as everyone but Stalin expected, it meant that Russia had become an ally, and Beatrice was called upon to write persuasive words about Britain's noble Soviet brothers-in-arms. he income added just enough more to maintain them in their mid-eighties.

In her bleak last years, at times when German bombs were not falling about the countryside, people from the Webbs' past sometimes visited Passfield Corner. Through BBC Radio they also kept in touch with the world now beyond their reach, and through the seldom-private quarrels of their remaining servants, upon whom they depended desperately, they realized even more acutely how fragile was their hold on life. At least Beatrice understood: disabled by his stroke, Sidney sat placidly in a chair and read novels, now and then mumbling a few words. Her one remaining kidney was failing, and she was in constant pain. "I shall die," she wrote in August 1942, "with my diary, pen and ink in a drawer by the side of my bed." And she did. On April 19, 1943 she set down a mystical experience in which the BBC abruptly stopped broadcasting, her cup of tea went cold, and everything quietly disappeared. Death would come like that, she hoped, "sudden, complete, as the wireless set was in its broadcast, and the fire and the electric light, the chairs and the cushions, and the kitchen, the dining-room, the study and the sitting-room." It was her last entry. Eleven days later she was dead.

In the MacKenzies' selections, the diaries read like an elegy to a vanished Britain. Begun in the optimistic late-Victorian afternoon, they close in the wartime twilight of privation and unfulfilled hopes. Beatrice Webb had visions of being a partner in a vast enterprise of social engineering. For her lasting reputation it was fortunate that she also kept a diary.