English instrument maker George Adams Junior (1750-1795) published An Essay on Vision in 1789, with a second edition appearing in 1792. The 153 page book (157 pages in the second edition) presented material on structure of the eye and the basic nature of vision and vision conditions, with an emphasis on the proper use and choice of spectacles for the "long sighted" and the "short-sighted." A brief biographical sketch of Adams is given, and the contents of the book are discussed, with presentation of excerpts relating to general optometric principles. The excerpts can serve to illustrate the state of optometric knowledge in the late eighteenth century.