News of the first civilized foot set down in the wilderness was always eagerly received at home; it indicated that the earth was manageable, and absolved the rest of human society of the need to prove it.

Nature seemed sublimely inexhaustible, like a normal NFL season. Then geophysical knowledge coincided with the conquests of man--the Laffer curve of exploration--and left everybody a bit grumpy. There was nothing left to discover. Skepticism about past exploits became as reflexive as adulation of current explorers: Those sepia-toned walrus-mustaches probably never got out of the igloo!

The author of this history of dubious exploration is himself a mountaineer, and a highly literate one, which adds vitality to an old, speculative sport of hero-reduction. Roberts points out that exploration lends itself to hoax and that any expedition can be misrepresented when witnesses are few, or a-mouldering in the bush. He seems free of the contemporary prejudice against the old Outward Bound walking machines who got to all the really difficult places ahead of us.

The low-tech accomplishments of the early explorers now seem somehow shabby, their fierce independence unseemly. They would certainly be difficult to package for the current media market. Imagine Abyssinian Bruce, tracer of the Blue Nile, being interviewed by Jane Pauley, or Peary muttering into a microphone held by a rictus in a red blazer, ". . . One giant dog sled for mankind."

Did Sebastian Cabot reach the Americas in the 16th century, or Father Hennepin the mouth of the Mississippi in the 17th? Probably not, though their claims were accepted at the time. Even James Bruce, the 18th-century Scottish laird who spent four years on the African continent and saw an incredible amount of exotic carnage, was initially praised.

However, Bruce's report that Abyssinians cut steaks off the flanks of living cows was too much for Englishmen (tales of cruelty to humans were all right). A satirical poem published at the time read:

Nor have I been where men (what loss, alas!)

Kill half a cow, and turn the rest to grass.

The foppish Boswell described him as a "curiosity." Samuel Johnson had no use for him. Bruce had actually seen the land that Johnson wrote about in "Rasselas," supposedly a translation of a Portuguese priest's African travels, and Johnson preferred ale house conjecture to muscular reality. They decided that Bruce was a liar before he could get into a quiet country grave, when in fact he was telling the truth.

Roberts finds common afflictions among hoaxers: the early loss of a parent, childhood infirmity and a strain of megalomania. Fortunately, exploration psychohistory -- Peary was not seeking Farthest North, he was searching for . . . his mother! -- is subordinated to the tales themselves.

"Captain" Samuel Adams, who claimed to have shot the Colorado River ahead of John Wesley Powell, belonged to the tradition of the American West, "full of liars and braggarts." He saw profit in recognition by the federal government, and in 1867 buncoed a tiny mining town into providing stores, muscle, and a handwoven flag for his descent of the river. His boats quickly came apart on the boulders, but that didn't deter Adams from claiming he had accomplished the trip, and lobbying Congress for money.

A more adept and determined hoaxer in the same tradition, Frederick Cook, falsely claimed in 1906 to have climbed Mount McKinley, the highest peak in North America. He took along a Montana rube willing to pose for a photograph on a nearby hillock, an undeniable fake when later compared with the real thing. In the meantime, Cook had pushed on to the North Pole, or rather, to the northern coast of Greenland, where he announced he had achieved 0 Degrees North, ahead of Peary.

Cook's Eskimo companions recanted, as did the Montana rube, and Cook died the object of deserved ridicule. Roberts asks why Cook, already a successful explorer before McKinley, turned flaky. "There is something in the life of more than one exploration hoaxer that yearns for the simplistic and the dramatic." He suggests that a need exists for dividing the world into friends and enemies, the ultimate gambit for the perambulatory paranoid.

Peary's and Byrd's polar exploits are by now numbingly familiar. Both were driven, conniving, often ungenerous men, according to Roberts. Peary's mother called him Bertie, and well into his middle age loaded him down with guilt before each expedition. Byrd drank cognac during some dangerous flights, and once had to be dumped into his bunk. He took all the credit (his pilot, Floyd Bennett, first flew over the North Pole in 1926, if anyone did), and apparently could not even navigate.

Both men attracted reputable champions, and remain heroes. The evidence suggests that both fell short of the Pole. Both intended to accomplish what they set out to do, and only claimed success, if that's the case, in the certain knowledge that they would not get another chance to be first -- a kind of fraud in extremis.

Donald Crowhurst, however, set out to fake a singlehanded circumnavigation of the earth solely for the money, a "solitary conspiracy against the world." Crowhurst, a squirrelly English mathematican given to seasickness, knew little about sailing when he entered the race in the mis-rigged Teignmouth Electron in 1967. Yet he spent most of the next year sailing around the South Atlantic, falsifying his log, sending radio messages claiming he was on the far side of the earth, and carrying on a colliloquy with the ghost of Albert Einstein.

Crowhurst would have sailed home to glory and financial solvency if he hadn't jumped overboard in the midst of a metaphysical deliberation.

The tendency to dismiss explorers suspected of hoax is unjustified, as is the lavish praise expended upon them before the evidence is in. "Captain" Adams did attempt, after all, to shoot the headwaters of the Colorado in a rigid boat. Cook, a lisping fraud to posterity, navigated the glacial corridor of Great Gorge and mushed around Ellesmere Island, no mean accomplishments.

Peary lost toes in what was a lifelong, magnificent obsession. Byrd had the guts to climb into a trimotor Fokker and wobble out over the drifting ice pack, with a fair chance of not returning. Even the mad Crowhurst reached the coast of Brazil.

They were all solitary, mostly sad efforts, far from the Barcalounger.