Identifying the source of the Nile fascinated the ancient world. Herodotus, Alexander the Great and the Emperor Nero all pondered how the river could flow unflagging through 1,200 miles of desert without the support of a single tributary. Yet not until the 19th century was the mystery solved. Drawing on new material available since Alan Moorehead’s classic and accessible ”The White Nile” published half a century ago, Jeal relates in this elegantly written and skillfully crafted book how a handful of Victorian explorers — Richard Burton, John Speke, James Grant, David Livingstone, Henry Stanley, Samuel Baker and his mistress, Florence von Sass — plunged into east and central Africa to uncover “the planet’s most elusive secret.”

Their motives were various — love of self, love of country, detestation of the slavery plaguing the region, and a desire to do good to Africa through Christianity, commerce and colonization. The rivalries among them were often fierce. In pursuit of their quest, they risked enslavement and death by illness, starvation and even cannibalism. They survived, as Jeal reminds us, only because of the help of numerous African interpreters, guards, guides, porters.

The sighting in 1858 by Burton and Speke of “an expanse of the lightest, softest blue” — Lake Tanganyika — was pivotal. Burton claimed the lake as the Nile’s source. Speke — correctly as it happened — proposed the more northerly Lake Victoria, which he visited alone after Burton fell ill. Jeal provides a compelling dissection of the rivalry between the egocentric Burton — who earlier had made the pilgrimage to Mecca disguised as a Muslim peddler — and the blue-eyed, “tawny-maned” Speke. Jeal ably defends Speke against the charge of betraying Burton by going alone to the Royal Geographical Society — the expedition’s sponsor — on returning to England in advance of Burton. He also suggests that Speke’s death in 1864 on a partridge shoot on the very eve of a “great Nile debate” at which he and Burton were to air their disagreements about the source of the Nile was accidental and not, as Burton claimed, suicide to avoid “the exposure of +[Speke’s] misstatements in regard to the Nile sources.”

Unsurprisingly, given Jeal’s previous well-received biographies of the missionary Livingstone and the journalist Stanley, the characters of these men are also well-drawn. Jeal traces the events and motives leading to their celebrated encounter near the shores of Lake Tanganyika in 1871. Livingstone had gone to Africa in 1865 in hopes of proving that Lake Tanganyika was — as Burton believed — the Nile’s source. He was a competitive man who found the prospect of being the one to solve the Nile mystery appealing. He also hoped his expedition would publicize the extent of the Arab slave trade and open up the continent to more benign influences. To Livingstone, Africa’s rivers — the Nile included — were “God’s Highways.”

For years there was no word of Livingstone, and many thought him dead. Stanley, an ambitious journalist backed by James Gordon Bennett, irascible owner of the New York Herald, hoped to make his fortune by tracking Livingstone down. In 1871 Stanley finally succeeded, though he probably didn’t greet the missionary with the famous words “Dr. Livingstone I presume.” Jeal shows how Stanley — born in 1841, the year Livingstone first went to Africa, and consigned to a Welsh workhouse after his family rejected him — had always yearned for a father figure and, in Livingstone, found him.

‘Explorers of the Nile: The Triumph and Tragedy of a Great Victorian Adventure’ by Tim Jeal (Yale University Press)

Together they traveled to Lake Tanganyika only to find it could not, after all, be the Nile’s source. Livingstone was by now exceedingly frail and suffering from numerous ailments — bleeding piles, rotting teeth and ulcerated feet to name but a few— but still determined to discover the Nile’s watershed. His death near Lake Bangweulu, after Stanley had returned to Britain, devastated the younger man, who believed that continuing the exploration was “a legacy left me by Livingstone.” Ironically, Stanley went on to prove in 1877 that Lake Victoria was indeed the Nile’s source, vindicating Speke and proving Livingstone, his “honorary father,” wrong.

As Stanley put it, Livingstone’s journals exposing the evils of slavery stimulated “the civilized nations . . . to extend their care and protection over the oppressed races of Africa.” However, as Jeal shows, such humanitarian arguments gave foreign governments a pretext to advance their territorial interests. Some explorers even became unwitting pawns in the “Scramble for Africa.” Stanley himself was duped by Leopold II of Belgium, whose eyes — tragically as it proved for the Congolese — were upon the Congo.

Jeal plausibly suggests that the establishment of British, French and German colonies within the region investigated by the Nile explorers saved indigenous peoples from annihilation by Arab slave traders. Other conclusions of his geopolitical analysis — for example, that Britain withdrew from the region too soon — are perhaps more debatable. The greatest strengths of this highly enjoyable and readable book are Jeal’s passion for his subject and his mastery of personalities as complex as the geography they battled to understand.

Diana Preston is the author of “The Dark Defile — Britain’s Catastrophic Invasion of Afghanistan, 1838-42,” to be published in 2012.

EXPLORERS OF THE NILE

The Triumph and Tragedy of a Great Victorian Adventure

By Tim Jeal

Yale Univ . 510 pp. $32.50