My first experience in this connection was quite interesting. A young girl had got a needle into her hand while she was playing about, and the surgeons were at a loss to know where the needle had lodged. We lost no time in producing X-rays which could penetrate the flesh of the hand, and reach the fluorescent screen on the other side. The bones of the hand blocked the way of our rays, but not so completely as the needle did. Hence we produced upon the screen a faint shadow of the flesh of the hand, a much deeper image of the bones, and a black shadow of the needle. This enabled the surgeon to see where the needle was hiding. Sometimes we were called upon to produce rays for detecting bullets in the flesh, or for showing the nature of a fractured bone. We were never surprised to find that our call was to detect a coin in the throat of a child, but in this connection a big surprise awaited some of us. I was not one of the party, but I have the information from some fellow-electrons. [Illustration: HOW ELECTRONS PRODUCE X-RAY IMAGES The upper photograph shows the X-ray apparatus in use. The operator is examining the bones of the lady's hand, which she places between the X-ray tube and the fluorescent screen. The rays pass through the flesh, but are obstructed by the bones, the rings, and the bangle, so that a shadowgraph or image is formed upon the screen, which becomes luminous where the rays succeed in reaching it. The actual examination is made in a dark room. Owing to the way X-ray photos are taken (by contact) the image is reversed in a photograph, so that a left looks like a right hand.] A party of electrons were present within an X-ray tube at a large hospital, when they were called upon to produce rays for examining the throat of a little girl. They had become so used to this call that they did not doubt there would be a coin in the child's throat. However, they lost no time in producing the penetrating rays, and you can imagine their surprise when they produced the image of a toy bicycle upon the screen. It seemed ridiculous that such a toy could have entered a child's throat. When we had shown the surgeons exactly where the toy was, they set to work to remove it. The electrons heard later that the operation was successful in every way. Every one was interested, and we were proud. I do not wish to appear boastful, but I wonder how many operations owe their success to these rays which we produce for man. It was natural that man should try if these searching rays could affect the chemicals upon a photographic plate, and we soon proved that they could. It made no difference to us whether man kept the plate sealed up in its light-proof envelope, or whether he placed the plate within a wooden box. These protecting covers offered no barrier to our rays. We produced shadowgraphs of any objects placed between our tube and the photographic plate.