Letter to Fox Talbot from Jean-Baptiste Biot, 13 February 1839. Written in French. Jean-Baptiste Biot (1774-1862) was the pioneer of polarimetry. William Henry Fox Talbot (1800-1877) invented the negative/positive proces for making photographs between 1835-39. Any number of prints could be made from the same shot by transferring the negative image on to special paper; these prints were called calotypes. Detail of back page letter.
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