Reprint of Researches on the theory of the principal phaenomena of photography in the daguerreotype process, by A. Claudet, from the London, Edinburgh, and Dublin philosophical magazine and journal of science for Nov. 1849; of Description of the daguerreotype process, or a summary of M. Gouraud's public lectures, according to the principles of M. Daguerre; with a description of a provisory method for taking human portraits, first published in 1840; and of A system of photography, containing an explicit detail of the whole process of daguerreotype, by S. D. Humphrey and M. Finley, first published in 1849.