At first glance this lesser known part of the telephone inventor's life seems crazy. Bell became obsessed with pyramids, building towers, buildings, boats, kites and eventually planes made entirely out of little tetrahedrons (triangular pyramids). Eventually setting up the Aerial Experiment Association, he built 3 tetrahedral kite planes where each pyramid frame component had 2 of its 4 sides covered in fabric.His obsession, however, was ingenious and is possibly feasible - that if you could fly a pyramid frame structure then by combining lots of them together you would be adding no more weight per unit of lift, so you could fly a structure of any size.Although only one of Bell's planes managed to fly under its own power, the tetrahedral frame structure was to become a much used component of high tech architecture more than half a century later, giving these images of the Victorian inventors a bizarre science fiction feel.