Gathmann - Air Propellers for Flying Machines, British Patent 18560 of 1907
A British patent specification of 1907-08, filed by the American inventor Louis Gathmann, covering air propellers for flying machines and printed as a drawing sheet for the Patent Office and engineers. The single plate carries line diagrams in black on aged paper: side and plan views of a framed aircraft, a circle of shaded fan blades, blade sections, and handwritten filing numbers.
