John C. Frémont, the Pathfinder, was a bright mathematician and cartographer, a persistent and courageous adventurer, a quixotic man with more ups and downs in a lifetime than the New York Stock Exchange suffers in a year. He was also stubborn - stirring a whirlwind of passion and controversy with his contemporaries and, since his death in 1890, with historians and biographers. According to some biographers, Frémont was the child of a penniless French émigré and a socially prominent Virginia woman, born in Savannah, Ga., in 1813. Others suggest he was born out of wedlock. Whatever the case, he grew up in poverty, but managed to gain admission to Charleston College where his genius for mathematics emerged. After a short stint as a professor of mathematics, Frémont joined the U.S. Topographical Corps and assisted America’s great cartographer, Joseph Nicollet, in the exploration of the Mississippi valley.