Bissel is a small village of the West Sahara. It lies next to a l.5-square-kilometer oasis , from where three days and nights are generally required to go out of the desert. However, before Ken Levin discovered it in 1926, none of the Bissel villagers had ever walked out of the desert. Reportedly, they were not unwilling to leave this barren land. Many had previously tried but failed, always somehow finding themselves back at the oasis after several days of trying to walk out. When interviewed by Ken Levin, an expert at the British Royal College of Sciences, the villagers explained that no matter which direction they walked it always brought them back to the village.Why couldn't the Bissel villagers walk out of the desert? Levin was very puzzled. He had, by himself, managed to walk north from the village and reach the nearest town in three and a half days. He decided to carry out an experiment to solve the mystery. He and a Bissel villager called Argutel, would walk out of the desert together. They prepared enough water for a half-a-month journey and two camels. But this time Ken Levin didn't bring his compass. Levin would follow Argutel. Ten days later, they had walked for about 500 miles but were still in the desert. On the 11th morning, an oasis came into their view. They were back at Bissel. Levin now understood why the Bissel people couldn't escape the desert. They had no knowledge of the North Star, which had for centuries provided sailors and other travelers with a point of direction. In the desert, if a person goes forward relying only on their senses, they will not be able to travel in a straight line. Rather they will travel in a very large circle and eventually track back to where they began. Levin explained to Argutel the function of the North Star and said, "As long as you rest in the daytime and walk towards the brightest star at night, you would be able to walk out of the desert." Argutel did as he was told. Three days later, he came to the edge of the desert. Now in the West Sahara, Bissel has become a bright pearl, where tens of thousands of tourists come every year. Argutel's bronze statue stands in the center of the town. On its base are the words:  _ . According to the passage, Ken Levin   _  .
knew Argutel before he came to the village came to Bissel to do experiments on behalf of his college became the first man to walk out of the desert from Bissel Village taught Bissel villagers knowledge of the North Star when he first arrived