Triangular Prism with Achromatic Lens, by Soleil, Paris, c. 1840

French achromatic lens and prism, c. 1840 by Soleil, Paris.

A triangular lens mounted vertically on a copper alloy tripod base, each foot can be adjusted by way of a screw. Mounted on an arm beneath the prism is an achromatic lens that can rotate.

Item 97 in J. Duboscq, Catalogue systématique des Appareils d'Optique (Paris 1864), p. 19 was a "Lentille achromatique montée sur un pied en cuivre, pour la projection des raies du spectre", and it is possible that the present instrument is an earlier version used for the same purpose.