| John Herschel Fig. 21. John Herschell [sic.] 1864 (published) Engraving Google Books LL/34347 Source: "Les merveilles de la science: ou Description populaire des inventions modernes" By Louis Figuier (Paris, Furne, Jouvet et Cie, Editeurs, 1864). This engraving is in the section on "La Photographie" p. 60
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