THE MEANS BY WHICH WE NOW SEE THE INVISIBLE.

Star (Christchurch), Issue 19034, 1 April 1930, Page 8

THE MEANS BY WHICH WE NOW SEE THE INVISIBLE.

To-Day’s Signed Article

Specially written for the “Star” By A. F. Tyler.

It was only a generation ago that Professor Konrad Roentgen, of Vienna, noticed the image of a key on a photographic plate he had exposed while out for a walk on the previous day. He knew he had not purposely photographed a key, so how could the image have been produced? It proved to be the image of a Rat key he was accustomed to use as a book marker in the laboratory where he had been experimenting with some vacuum tubes.

Something must have passed from the vacuum tube through that book, casting an image of the key on the photographic plate upon which the book had been lying. He made a trial exposure, and sure enough, the effect was reproduced by some form of light coming from the glass vacuum tube, passing through the book and affecting the photographic plate on the opposite side. Not knowing what kind of light it was he called it the “X-ray.” Medical Uses of X-ray. In the brief period of thirty-four 3 r ears since Roentgen’s discovery, x-rays have become almost a househld word. Most of you, I am sure, have had some personal contact with the medical uses of x-rays, such as x-ray examinations for fractures and x-ray examinations of teeth, lungs, stomach and many other parts of the human body ai» well as x-ray treatments for diseases. You have doubtless noticed that an x-ray picture is different from a photograph in that the photograph shows that portion of the body that can be seen while the x-raj-s reveal that which is not visible. This is possible because the x-rays pass through the object, casting a silhouette on the film. As they pass through they reveal a difference in density and form, only, because of the fact that the more dense structures stop more of the x-rays than the less dense structures do. In way the bones cast a light image on the' film while the flesh casts a darker image, the silver in the emulsion on the film becomes darker in places in which the most light strikes. The bones, which contain much/ mineral salts, can thus be distinguished from the flesh, which contains less mineral. The heart can be distinguished because it is more dense than the air-filled lungs which surround it. See Heart Beating. It is not only possible to make x-ray pictures of the human body and other objects, but by proper technique one can watch the heart beat and the stomach writhe as 41 empties the food into the bowel. In order to see through the body one must be in an absolutely dark room long enough for the eyes to become dilated like cats’ eyes at night. This is necessary because the x-rays themselves cannot really be seen by the human eye, but when they pass through an object, striking a fluorescent screen, the screen gives off a faint bluish light which can be seen provided the work is done in darkness and the pupils of the eyes are dilated. . Not only are x-rays used to examine the human body, but they are used to treat

many diseases, such as cancer, skin disease and fibroid tumours. By proper technique in treatment by x-rays, the growths can be killed while the surrounding healthy tissue is not injured. X-rays are used for many purposes outside the field of medicine. They are used in the study of biology, geology, chemistry, in art, in veterinary surgery, in the steel industry, in the detection of contraband of war and in medicolegal problems. X-ray of Flowers. Ordinarily one would not think an x-ray picture could be made of flowers, yet the results are beautiful to behold, for all the inner markings are revealed clearly. In the same way one can study the anatomy of the lower forms of animal life and the structure of rocks. In recent years, a method has been devised for making chemical analyses by x-rays. The unknown substance is placed in a specially prepared machine and x-rays are passed through it. Bach substance in the unknown casts a line on the photographic film characteristic of that substance. By comparing this x-ray picture with those of known substances the chemicals can be identified. The process is thus much Simpler and saves much time as compared with the older laborious methods. A method has. also been found for making x-ray pictures of steel castings of several inches in thickness. This is used to detect flaws in heavy steel castings before they are put into actual service. In this manner thousands of pounds and many human lives are saved. Serves the Plumber. Recent developments have made the x-rays do service for the plumber and electrician. A small portable instrument is taken to the place at which work is being done and, with the x-ray tube on one side of a wall and the observer on the opposite side, pipes and wires buried in the wall may be definitely located before work is started. One of the most recent developments is in x-ray examination of materials used in road and building construction. By applying the same principles used in making chemical analyses, various materials such as cement can be identified. Not only can cement be distinguished from sand but various cements coming from different localities can be recognised, because the individual characteristics of each brand are distinctly revealed by the method of x-ray analysis developed by engineering experts. (Anglo-American N.S. Copyright.)