A Frenchman, named Fontamen, wrote an imaginary voyage to a strange country, and among other things he said that objects were reflected upon the water and when the water was frozen the images were retained. So this idea of certain surfaces being capable of receiving impressions by means of light was very ancient. There was another Frenchman, named Devique Delaroche, who made a still more curious statement. In 1760 he wrote a book in which his hero is wrecked upon a strange coast, and the spirits of that place showed him how to make pictures, as he called it, “painted by nature.” It is not quite sure what he means, but his words are something like these: “You know,” says his guide, “that rays of light are reflected from different bodies and form pictures. The spirits have sought to fix these pictures, and have a subtle matter by which these pictures are formed in the twinkling of an eye. They coat canvas with this peculiar matter, and hold it before the object.” The manner of holding it is not stated. “The canvas is then removed to a dark place and in an hour the impression is dry and you have a picture, the more precious in that no art can imitate its truthfulness.” These words were written one hundred and fifty years ago. This, as far as we know, was purely imagination; yet the idea--the germ of photography--was there. We shall presently see that this flight of fancy on the part of Delaroche was very near the truth, and foretold what has since become possible, and only a very short time after he said it. As time went on and observations of men became more definite, we obtain records of facts that were noted with regard to the action of light upon certain chemical compounds. You know those old alchemists had queer ideas, one in regard to their elixir of life, and another that they could turn the baser metals into gold. They discovered a material in the silver mines of the Hartz Mountains which they called “luna cornea.” The word luna was at that time applied to silver. Luna cornea was horn silver--what we know to-day as silver chloride. They noted that when this was first brought from the mine it was white and that after it had been exposed to the air and the sunlight it turned black, and they also noticed that it was only the surface that turned black--that if they scraped the surface off it was white underneath. They also found that if they kept it in the mine it did not get black. This observation was made about 1550 by Frobrishes, one of the early workers in chemistry; but you must remember that they were not studying the action of light upon this substance. Their sole object was the turning of the baser metals into gold, and therefore they did not pay much attention to this idea, although this fact was placed on record.