Alexis-Marie de Rochon (1741-1817) was a French astronomer and physicist who, in 1776, devised a “diasporameter” for measuring the dispersion of prisms of various substances. This unsigned example was probably made in Paris in the mid-nineteenth century.
Ref: Maurice Daumas, Scientific Instruments in the Seventeenth and Eighteenth Centuries (New York, 1972), p. 271.
Lerebours et Secretan, Catalogue et Prix des Instruments (Paris, 1853), pp. 34-35.
Rochon, Receuil des Mémoires sur la Mécanique et de la Physique (Paris, 1783).