In 1869, traffic in Manhattan was a nightmare.  It's not so great today, but it could be a lot worse.  Broadway, the main north/south artery, was regularly clogged with horse carts, pedestrians and omnibuses, slowly making their way up and down the island.  The avenues of New York, which also run north to south, weren't much better.  There had to be a better way.  A train would make sense, except that the city was so crowded, there was nowhere to lay the tracks.  An underground train would be great, but the only engines available at the time were steam engines, which give off a lot of smoke.  An underground train would be impossible to adequately ventilate. Alfred Ely Beach An inventor from Springfield, Massachusetts named Alfred Ely Beach thought he had a solution.  He conceived what he called the Beach Pneumatic Transit, which he proposed would be New York's first subway system.  He imagined a series of underground cars that would be...