The landscape after Gashua became flat scrub, offering long views in a palette of tans, browns, and dabs of dusty green. Nasiru Datti said it could be farmland but had fallen into disuse as the government ignored everything except oil. The land was also abandoned when Barth traveled through here. The cause then was slave raiders. Barth called the waste shameful, and blamed the greed and apathy of Bornu’s leaders. “Even the best of these mighty men,” he wrote, “cares more for the silver ornaments of his numerous wives than for the welfare of his people.”

We began passing watering places bunched with cattle. Some were community wells, some were national. The national water was free. At community wells, there was a fee. We stopped at a place where Fulani nomads were watering their herd. The well was stone-lined, three feet in diameter, and 40 feet deep. A teepee of logs and big wooden pulleys stood over it. The nomads attached one end of a rope to a plastic bucket and the other end to a camel, which hauled up the water with help from the men. They poured it into metal canisters for the jostling cattle.

The men were quick and animated. They wore drab dirty clothing, though one of them sported the traditional conical Fulani hat. The women, in brightly patterned robes, carried themselves elegantly amidst the cows and mud. “They would make good wives,” said Nasiru Wada, partly joking. “They work hard, and they would walk to Gashua and never call a cab.”

Nomads still come to Kano to sell natron or dates or camel-milk cheese, he added. They buy indigo, head scarves, sugar, and tea. As in Barth’s time, they roam freely across the landscape. “No one would stop them,” said Nasiru Datti.

Explorers and nomads share some traits: restlessness, constant movement, the austerities of a portable way of life that requires hauling one’s food, shelter, and belongings from place to place. It’s a hard existence, which is why Africans were often suspicious about the arrival of itinerant white men who claimed to have left their families and traveled thousands of miles, risking death under harsh conditions, for no reason except knowledge. To most Africans, including nomads, that sounded crazy. They had an excellent point.

“The notion of traveling for curiosity was new to him,” wrote the explorer Mungo Park about a wary African ruler. “He thought it impossible, he said, that any man in his senses would undertake so dangerous a journey merely to look at the country and its inhabitants.”

More than once, Barth set off alarms when he told African officials that he was visiting their territory not to buy or sell, but solely to learn about their history, customs, and beliefs. Surely, assumed many of these officials, this was a ruse to steal trade secrets, or a ploy to scout the country in preparation for an invasion. (This paranoia would eventually be justified when European nations carved up the continent among themselves.) In Timbuktu, the Moorish merchants who controlled the trade between the desert and the Mediterranean believed that Barth and the British were plotting to take over their lucrative trade, so they plotted Barth’s death.

Nomads are born into their itinerant life, but explorers choose it. That’s why, depending on one’s point of view, explorers look heroic or half-cracked (and are often both). From any perspective, they were mindboggling.

Examples are as numerous as flies around a caravan: Mungo Park, while searching for the Niger, dying of thirst after being plundered, stripped, and abandoned—and then returning for a second attempt. Alexander Gordon Laing, trying for Timbuktu, left for dead by Tuaregs in the Sahara, with five severe lacerations on top of his head, four across his temples, one through his cheek and ear, and another “dreadful gash” on the back of his neck—and then deciding to continue towards Timbuktu anyway. Richard Burton, seeking the source of the Nile, skewered through the mouth with a spear, his tongue so ulcerated he couldn’t speak and his body so wasted by fever he couldn’t walk unsupported for 11 months.

And why? For adventure, certainly. For glory, if they survived. All wanted to solve some geographical riddle and claim the honor for their country and themselves. Barth, like the rest, endured horrible sufferings and dangers, in his case for the sake of scientific discovery. Such perseverance, kept up for more than five years and 10,000 miles, verges on devotion.