Slinky's a helix-shaped toy that can travel down stairs end-over-end as it stretches and re-forms itself with the aid of gravity and its own momentum. The toy was invented and developed by naval engineer Richard James in the early 1940s and demonstrated at Gimbels department store in Philadelphia, Pennsylvania in November 1945. The toy was a hit, selling its entire inventory of 400 units in ninety minutes. James and his wife Betty formed James Industries in Philadelphia to manufacture Slinky a… (More on Slinky)