Complex sentence: While MacMillan certainly existed and rode some velocipede, he didn't ride the velocipedes published by Thomas McCall twenty years later in 1869, as all rear-wheel driven velocipedes were a reaction to the Michaux velocipede.
Split into simpler sentences: While MacMillan certainly existed and rode some velocipede, he didn't ride the velocipedes published by Thomas McCall twenty years later in 1869. All rear-wheel driven velocipedes were a reaction to the Michaux velocipede.