When you light a candle it burns, because the lighted wick heats the wax sufficiently to turn it into gases, which mix with the oxygen in the air and produce fire in the form of light. You know it is not easy to light a candle quickly. You must hold the lighted match to the wick until the wax begins to melt and change to gases. As long as the wax continues hot enough to melt and turn to gas the candle will burn until all burned up; but if there is a break in the continuous process of changing the wax to gas, the light will go out. Now, when you blow at the lighted candle, you blow the gases which feed the flame away from the lighted wick, and this makes a break in the continuous flow of gas from the wax to taper, and the light goes out. [Illustration] The Story in a Photograph How Does a Camera Take a Picture? When we look upon the surface of a mirror we see the image of ourself and our surroundings. The extent of the view depends upon the size of the mirror and the distance we are standing from it. If we hold the mirror close to our face we see only the face, or perhaps but a portion of it, and the farther away we are the more the mirror will reflect, only, of course, the various images will be smaller. The mirror reflecting exactly what the eye sees, without doubt had a great influence in inducing the experiments that resulted in the process we call photography. The taking of a photograph with a camera may in a way be compared with the action of your eyes, when you gaze upon your reflection in a mirror, or look at any object or view. Any object in a light strong enough to render it visible will reflect rays of light from every point. Now, the eye contains a lens very similar in form to that used in a camera. This lens collects the rays of light reflected from the object looked at and brings them to a focus in the back of the eye, forming an image or picture of whatever we see, just as the mirror collects the rays of light and reflects them back through the lens of the eye. Certain nerves transmit the impression of the image so focused in the back of the eye to the brain and we experience the sensation of sight. What Is the Eye of the Camera? The lens is the eye of the camera, and the process we call photography is the method employed to make permanent the image the eye or lens of the camera presents to a sensitive surface within the camera. Fig. 1 shows a simple form of camera, it being merely a light tight box with a lens fitted to the front, and a means for holding a sensitive plate at the back, the plate being placed at just the right distance to focus the rays of light admitted through the lens in exactly the same manner as the rays of light pass through the lens of the eye and come to a focus in the back part of the eye. Now, if we could look inside the camera we would note that the image was inverted, or upside down. Fig. 2 will explain this.