The invention and early manufacture of bifocals

Benjamin Franklin, who died 200 years ago, is generally credited with the invention of bifocals. However, serious historians have from time to time produced evidence to suggest that others may have preceded him in the invention. This historical article includes correspondence from George Whatley, a London philanthropist, and John Fenno, editor of The Gazette of the United States, which convincingly documents that Franklin invented bifocals, perhaps 50 years earlier than has been generally thought. Appendices detail the many difficulties encountered in the early manufacture of bifocals.