Note on vortices on their relation to the lift of airfoils
This is a 1924 technical note from the NASA Technical Reports Server on vortices and the lift of airfoils, a record with no named author or intended readership beyond aeronautical study. Its two figures are plain line diagrams: a cube-like box of circulating arrows drawn in oblique projection, and a ring with a small inner circle marked by a curved arrow showing rotation. A designer could take from them a clean schematic language of circulation and flow direction, useful for abstract diagrams of rotation.
