THE FIRST BALLOON FLIGHT in America lifted off from Philadelphia in 1793, and the 100th anniversary of the event prompted a reawakening of interest locally. That year a group of Philadelphians banded together to build a series of balloons, the last and largest of which, christened Ben Franklin , began flights in 1907. By chance, the group acquired the services of an official photographer, William Jennings. Jennings was eager to shoot views of Philadelphia from the air, and he finally talked his way onto his first flight by offering to pay all costs. Once aloft, Jennings described himself as a “Photo Birdman, rushing through Cloudland.” His aerial views turned out well, but the photographs he took of the flights themselves are more wonderful still. In a scrapbook he titled “The Evolution of Aviation,” Jennings’s pictures document one man’s delight at learning to fly.