The result of this gelatine-bromide of silver process is this: that we can have plates in packages. We can put these emulsion plates and carry them off where we please, and, what is still more important, we can put the emulsion upon very thin material, and I have here (exhibiting them) thin sheets of celluloid upon which this emulsion has been spread and pictures taken. That is not all, either; they can make it still thinner (producing small camera) they can put it on a roll and in this camera is one of those rolls, and in that box I can take a hundred pictures without reloading the instrument. The way it is done, I, when I want to produce a new surface, simply wind the old one off with this winding machine. There is an opening at the front of the camera. Press just below this, so, and you have the picture. Now just wind the film off and you are ready for the next picture. Now pull it again, and this is so easy that some manufacturers say: “You simply push the button and we do the rest for you.” That is nonsense, they don’t do the “rest” for you. A friend of mine took one of these to Europe, and with it a dozen rolls of film, all of which he used. When he returned he sent them to the manufacturers and I think he got about twelve pictures back. Not every time you press the button is a good picture produced. You have to know a little bit about the science and use a little judgment. Such is the state of photography to-day that this material can be spread upon any kind of transparent surface. In the case of plate, they are put in holders like this, generally only two on each side, and slipped into this frame in a dark room, in which no light can be used except one emitted through a deep red chimney. (The professor here exhibited such a chimney.) Then, the material that is used for developing these pictures is somewhat different from the old method. We use organic compounds, alkaline solutions, and organic matters capable of taking up oxygen. These organic materials, in conjunction with some alkali, are capable of taking up oxygen. They produce a disoxygenizing action. After dipping, that gives you the negative. The prints are made in a variety of ways. The facility with which these apparati can be used has led to an enormous variety. You can have an apparatus something like that, or something like this, which is smaller.