On angular aperture of objectives for the microscope : read before the Microscopical Congress at Indianapolis, Ind., August 15th, 1878 (1880)
Blackham, Geo. E. (George E.), National Microscopical Congress (1878 : Indianapolis, Ind.) · New York : Industrial Publication Co. · leaf 63
I Figure 17. Balsam Mount. Scale X 20. Refraction of Rays passing from Crown Glass to Glycerine. The dotted lines represent the course the Rays would take if the Glycerine were replaced by Air. … Geo. E. Jilackham, M.D., Bel.
Microscopy · Lenses · Geometrical optics
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.