A new book debunks many of the widely-held beliefs about the late polar explorer, Rear Admiral Richard E. Byrd, contending that much of the Navy saw him as a "vain, mystical egocentric" whose career was boosted by his brother, head of Virginia's Byrd machine.

The book, a chronicle of Byrd's final Antarctic expedition, paints the adventurer as a "political admiral" who took advantage of his brother's position in the Senate to further his own ambitions and polar schemes.

Byrd, widely heralded as one of the nation's top military explorers at the time of his death in 1957, skillfully used a mixture of "showmanship and huckstering" to project that image, according to Leslie A. Rose, a State Department polar affairs expert and author of the new book, "Assault on Eternity."

"Don't get me wrong, I thought the world of Byrd," said Rose, a Northern Virginia resident and a participant in a 1956 Antartic expedition, in an interview yesterday. "But I don't believe in cardboard characters."

Until now virtually all that has been written about Byrd has been in glowing praise of his exploits at being the first aviator to fly over both the North and South Poles and his expeditions to the White Continent, which won him the title "Admiral of the Antartic."

Rose notes in his new book that Byrd immodestly bestowed his own title on himself during one of his polar adventures. "I am," he announced, "the mayor of this place."

Byrd, the golden-haired, high-cheeked younger brother of Harry, had a "stormy marriage" with the Navy despite the flying exploits that Rose says made him a genuine hero early in his military career.

Those drawn close to Byrd during his expeditions were totally devoted to him -- a fact that Rose says may account for the adoration he received throughout his life. Even now, 23 years after his death, Rose said he found few of the admiral's old friends willing to speak against him publicly. Access to his personal papers remains guarded by his family.

Rose's book, published by a small nautical publishing house in Annapolis, was intended to be a biography of Byrd, but Rose said that he had to cut those plans short when he was denied acess to the admiral's papers. Instead, he produced a history of "Operation Highjump," a massive post-World War II expedition that Byrd led to the Antarctic in 1946-47.

The book, nonetheless, devotes considerable attention to the admiral and suggests that during an earlier 1934 expedition his exposure to noxious fumes from a small heater in a 9-by-13-foot shack under the Ross Ice Shelf may have "subsequently weakened the man's critical faculties." It also says that during another expedition he "apparently experienced what can only be described as a mystical experience," when he claims to have heard "a gentle rhythm . . . the music of the spheres, perhaps!" coming from the skies in 80-degree below zero weather.

Yet, for all the glory his polar exploits brought the Navy and the nation, Rose says Byrd had enemies within the service who saw him as a man whose political connections helped him leap to higher rank over others on the basis of "grandstanding [that was] galling to the point of fury."

"He would use any tactic, including the formidable charm of the 'southern gentleman' to get his way," Rose wrote. "If thwarted, he could be 'meaner than a barrel of pickled a------s," according to one who had to brave the admiral's wrath on at least one important occasion."

Byrd, for example, challenged columnist Drew Pearson's assertion that the admiral had quarreled with a photographer who disputed his claims to having mapped several thousand square miles of Antarctica. The Navy, Rose noted, later backed off from some of the admiral's claims.

If Sen. Byrd's political clout helped his brother with the Hoover and Roosevelt White House, then the chill that developed between the Senator and Harry Truman gave his brother no assistance at the end of Operation Highjump. When Byrd returned to the Washington Navy Yard in 1947, Secretary of the Navy James Forrestal greeted him. The welcome was hardly warm and it wasn't until the ceremony was over that someone discovered that three penguins Byrd had brought back to the capital had wandered away unnoticed.

It was clear then, if not before, that Byrd's polar career had peaked.