http://forgotten-ny.com/ This picture is also from the website: Boynton Place and Avenue X is near the Avenue X stop on the Culver Line and is very near the entrance to the Coney Island Shops and Yards. As it was stated elsewhere, this area (Gravesend-Coney Island) is very rich in transportation history and it is only fitting that Boynton Place should be near a rapid transit facitlity, either a yard or a station. Perhaps his experimental train ran through this very area?
THE BOYNTON UNICYCLE RAILROAD.Scientific American, March 28, 1891
During several weeks last summer there were in regular and continuous operation, in railway passenger service, the locomotive and cars shown in the lower view herewith presented, the service being between Gravesend and Coney Island, on an abandoned section of an old standard gauge track of the Sea Beach and Brighton Railroad. The locomotive weighs nine tons, and has two 10 by 12 inch cylinders, the piston rods of both being Connected with cranks on each side the single six-foot driving wheel, and the front of the locomotive being also supported by two 38-inch pony wheels, one behind the other. These wheels have double flanges, to contact with either side of the track rail, as also have similarly arranged pairs of 38-inch wheels arranged under and housed in the floors near each end of the cars.