Johnson's natural philosophy and key to philosophical charts : illustrated with 500 cuts; being reduced photographic copies of all the diagrams contained in the author's philosophical series of indestructible school charts ; for the use of schools and families
A school physics and astronomy textbook by Frank G. Johnson, published in Chicago by A.H. Andrews in 1878, serving as the key to his wall charts for classroom and home teaching. The 397 cuts are photographic reductions of those charts, printed as white line on solid black: orbits, lens and eye ray paths, magnetic fields, and lettered apparatus, usable as high-contrast negative diagrams.
