ED O'LOUGHLINreviews Explorers of the Nile: The Triumph and Tragedy of a Great Victorian AdventureBy Tim Jeal Faber and Faber, 528pp. £25

IN 1948 A LANCASTER aircraft of the Canadian air force was flying north of Hudson Bay when it photographed a previously unknown island, roughly a ninth the size of Ireland. This low, uninhabited stretch of permafrost was the last major land mass to be added to the map of our planet; it was named for Prince Charles, who was born that year.

It seems strange that the age of exploration limped to an end so recently, in the postwar era, well within lucid living memory. We are already so used to a world that is mapped, photographed, surveyed and divided; we know where we are, cartographically speaking.

The great unknown is now only a memory, or a figure of speech. People still have adventures with geography – Ranulph Fiennes and his treks over deserts and ice caps, Tim Butcher and his hair-raising journeys of rediscovery through African failed states – but they know where they’re going, if not that they’ll get there alive.

In Explorers of the Nile, the British historian and novelist Tim Jeal takes us back to a time when maps were still splashed with mysterious blanks. In his deft, well-paced narrative he retells the interlocking stories of the handful of British men (and one Romanian woman) who, in the reign of Victoria, solved a mystery that had puzzled scholars since the Bronze Age: where in the remote south of Africa did the Nile rise, and how did it manage to flood the land of Egypt every year, despite having already crossed thousands of kilometres of desert?

For Jeal this is familiar ground: he has already published biographies of two of his new book’s protagonists, David Livingstone and Henry Morton Stanley. The latter book, published in 2007, was much more sympathetic to its controversial subject than had previously been fashionable, and here Jeal repeats its central thesis: that Stanley was more humane and much less racist, ruthless and violent than he had been portrayed, not least because of his own ill-judged and lurid accounts of his adventures.

Similarly, Explorers of the Nilere-examines the ill-starred partnership of the Indian army officers Richard Burton and John Hanning Speke, who, in the course of a joint expedition in 1856-59, separately discovered Lake Tanganyika and Lake Victoria (for western science, that is: Africans already knew they were there). Upon their return the pair fell out, permanently and poisonously, over which lake would prove to be the source of the Nile, and who should get the credit.

Although Speke was posthumously found to be correct (retrospective spoiler alert: Lake Victoria), posterity has nonetheless sided with Burton. A dark, poetic renegade and gifted linguist, Burton had translated (and vigorously researched) the Kama Sutra, and made an early play for fame by visiting the forbidden Muslim shrine of Mecca disguised as a pilgrim. (He was not, however, the first Christian to do so.)

Compared with this bohemian, Byronic rebel, Speke seems inhibited and square, a tongue-tied, uncultured bachelor whose chief recreation was big-game shooting. Speke also proved inept at appeasing the “armchair geographers” of the Royal Geographical Society, who downgraded his standing accordingly.

Jeal makes a convincing case for Speke’s rehabilitation, showing that he was not only the better man and explorer but also far more decent in his treatment of porters and servants, and more concerned about the fate of the fragile African societies whose territories they traversed. In contrast, Burton despised Africans and cared little for the cause celebre that, officially at least, drove Europe’s exploration of 19th-century Africa.

This was the campaign, championed by the missionary-explorer Livingstone, to save native African tribes from the Portuguese and Arab-Swahili slave traders who were devastating the continent. But Livingstone, no less than his younger rivals, was also driven by the raw lust for discovery and glory. His final journey, which cost him his life, was a desperate attempt to outflank the claims of both Speke and Burton by proving that the Nile rose farther south than either of his rivals’ discoveries. It doesn’t.

Jeal succeeds colourfully in putting us in the shoes of his staggering, starved, malarial male heroes. We may think that Stanley was wrong to shoot his way through the tribesmen who tried to block his canoes on Lake Victoria, but we can understand why, having come all that way, he was driven to do it.

The book is less convincing with the remarkable character of Florence von Sass. Purchased from a Turkish slave market by the explorer Samuel Baker, this 19-year-old Romanian beauty accompanied him on his first journey up the Nile as an unacknowledged and disposable mistress. After four years of shared sickness, travel and dire peril, she had so endeared herself to Baker that he brought her home to Britain and officially married her (though not, Jeal reveals, without first having contemplated dumping her in Khartoum). Yet despite citing her diaries as a source, Jeal offers little insight into her motives and feelings, which seems an omission when set against his empathetic treatment of his more famous male subjects.

The book also loses some pace and direction in its final quarter when, having settled the question of the sources of the Nile, it morphs into a polemical discussion of the subsequent history of Sudan, Uganda and Kenya, right up to the present day. This has a tacked-on feel.

While Jeal’s main narrative betrays no condescension to its individual African subjects, his coda suggests a little too much home-team sympathy for the notion that the British, unlike the Germans and French, were drawn into seizing African colonies by misplaced humanitarian concern rather than, say, the lust for power, glory and wealth.

As Commoro, a skeptical Latuka chief, told the blustering Samuel Baker: “Most people are bad. If they are strong, they take from the weak. The good people are all weak. They are good because they are not strong enough to be bad.”

Ed O'Loughlin is a former Africa correspondent for The Irish Timesand Middle East correspondent for the Sydney Morning Herald.His second novel, Toploader, was published this year