This image, taken between 1885 and 1890, shows a pocket daguerreotype that belonged to American General John A. Logan. The two circular daguerreotypes enclosed in this small frame are of a Mrs. Logan and a Mrs. Tucker, who must have been very important to General Logan. Daguerreotypes were produced on metal plates using silver iodine and bromide to make the plate sensitive to light and were developed with mercury vapors and ultimately fixed with salt and water. Daguerreotypes have since become obsolete due to this rigorous process and because the vapors from the mercury are very toxic. Despite these difficulties and dangers, the daguerreotype became a popular alternative to the expensive painted miniature and a marvel for its extraordinary detail. Professional painters needed great skill to produce something this small in size with anywhere close to this much detail and therefore their services were very expensive. Daguerreotypes have extremely high resolution, even by our modern standards, because of the use of these mercury fumes, which was another contributing factor as to why photographers would use this technique despite the potential danger it posed to the health of the person developing the image. There was no negative produced, so daguerreotypes are unique images that must be rephotographed by other means to be copied. And while the salt and water did fix the photographic image onto the plate, over time it would fade and discolor unless the daguerreotype was properly kept behind glass in an airtight case.