Theory and practice of the electric telegraph; a manual for operators and students
A technical manual on telegraphy by Charles Henry Churchill, published in Oberlin, Ohio, in 1875 for telegraph operators and students. The wood engravings show relays, sounders, induction coils, batteries and magnets on plinth bases, drawn in fine parallel hatching, with a few hands holding bar magnets or keys — useful as line-art apparatus silhouettes and hatching textures.
