are almost never on polished metal and do not exhibit this peculiar characteristic of appearing positive or negative depending on the lighting and reflections. Competition with Talbot Unbeknownst to either inventor, Daguerre's developmental work in the mid-1830s coincided with photographic experiments being conducted by William Henry Fox Talbot in England. Talbot had succeeded in producing a "sensitive paper" impregnated with silver chloride and capturing small camera images on it in the summer of 1835, though he did not publicly reveal this until January 1839. Talbot was unaware that Daguerre's late partner Niépce had obtained similar small camera images on silver-chloride-coated paper nearly twenty years earlier. Niépce could find no way to keep them from darkening all over when exposed to light for viewing and had therefore turned away from silver salts to experiment with other substances such as bitumen. Talbot chemically stabilized his images to withstand subsequent inspection in daylight by treating them with a strong solution of common salt. When the first reports of the French Academy of Sciences announcement of Daguerre's invention reached Talbot, with no details about the exact nature of the images or the process itself, he assumed that methods similar to his own must have been used, and promptly wrote an open letter to the Academy claiming priority of invention. Although it soon became apparent that Daguerre's process was very unlike his own, Talbot had been stimulated to resume his long-discontinued photographic experiments. The developed out daguerreotype process only required an exposure sufficient to create a very faint or completely invisible latent image which was then chemically developed to full visibility. Talbot's earlier "sensitive paper" (now known as "salted paper") process was a printed out process that required prolonged exposure in the camera until the image was fully formed, but his later calotype (also known as talbotype) paper negative process, introduced in 1841, also used latent image development, greatly reducing the exposure needed, and making it competitive with the daguerreotype. Daguerre's agent Miles Berry applied for a British patent under the instruction of Daguerre just days before France declared the invention "free to the world". The United Kingdom was thereby uniquely denied France's free gift, and became the only country where the payment of license fees was required. This had the effect of inhibiting the spread of the process there, to the eventual advantage of competing processes which were subsequently introduced into England. Antoine Claudet