Elementary optics and applications to fire control instruments
A 1922 U.S. Army Ordnance Department training manual on elementary optics and its use in gunnery fire-control instruments, printed by the Government Printing Office in Washington for artillery officers and technicians. The plates are line ray-diagrams: labelled light paths bouncing off hatched mirror surfaces, lenses with focal-length brackets, angles of incidence and reflection, and lettered points strung across thin rules.
