them fade, until he went one day to a closet where he had a lot of these pictures stored, and he was delighted to see that the picture of a certain monument (I think it was) that he had made he thought on that plate some time before, and it was a good picture and a permanent picture. How it came about puzzled him a great deal. In looking around the closet where these pictures were exposed--where these plates were stored--he found that for some reason or other the bottle of mercury had been broken, and he tried almost every imaginable material in the closet, and at last it struck him it might be mercury. Well, he put some mercury on the plate and he ruined it. “Well, no,” he says, “it is not mercury but mercury in a very fine state. I wonder if it is the _Vapor of Mercury_?” He tried it and found that it was. That led to the development of the daguerreotype. Then all he did with a plate was to put it into a vessel with a few drops of mercury, and underneath a little spirit lamp. Then he would put the plate in and watch the heat (some now have a thermometer) and he would just pick it up every once in a while to see how it is developing. That process gave to him the first picture, the daguerreotype, and those are to-day the handsomest pictures ever made by photography. I have two or three of them which are partly spoiled, but to-day they far surpass anything we have ever since done in the science of photography. After the mercury process, it was very easy to wash the plate off. The object of the development was this: that where the light had acted there the mercury seemed to take hold and bring out the picture. Where the light had not acted you could dissolve the silver surface off with cyanide of potassium, which was generally used. But, if you will look at this old-fashioned daguerreotype, you will see that you had to look at them in a certain light; otherwise, you could see nothing. Sometime afterwards a man named Fitsherbert, a Frenchman, conceived the idea of changing this peculiar picture in silver plate into a gold picture. In other words, he put into the plate a little chloride of gold and produced a daguerreotype which can be seen pretty clearly by looking squarely at it.