Jacob Christian Hansen Ellehammer (1871-1946) was a Danish watchmaker and inventor who made early contributions to powered flight. Unaware of the Wright brothers' success a couple of years earlier, Ellehammer worked in isolation to invent a means of flight, a feat he achieved in a "semi-biplane" on September 12, 1906. He soon shifted his attention to vertical flight craft, succeeding in 1912 in hopping along above ground in an experimental helicopter. This photograph is part of an album documenting Ellehammer's experiments in aviation between 1905 and 1920. Ellehammer's later inventions included a successful triplane. His helicopter was a coaxial machine.