Letter, from Charles Wheatstone to Sir John Herschel, dated at 20 Conduit St. Autograph letter signed by sender. Invites John Frederick William Herschel to Kew Green to see Francis Bauer's plates etched by J. N. Niepce's photographic process. Perhaps L. J. M. Daguerre assumes more credit than is due. Heard Niepce visited London in 1826, but his paper was rejected by Royal Society [of London] at W. H. Wollaston's urging. 25 February 1839