A generation ago, the Test Tube was the symbol of Science. Present now is the era of the Vacuum Tube. While tubes with everything imaginable in them are still used in laboratory research, tubes with nothing in them are used in radio as amplifiers, in medicine as a source of X-rays, in the laboratory to photograph molecules, as guns to bombard and break down atoms. Last week new tube developments were reported:
Millikan Tube. Members of the Radiological Society of North America meeting in Pasadena gave Dr. Robert Andrews Millikan, chairman of California Institute of Technology, a gold medal for a powerful X-ray source developed in his laboratories. The new 650,000-volt tube, the work of Dr. E. C. Lauritsen, is the most powerful ever demonstrated. Dr. William David Coolidge in General Electric Laboratories, Schenectady, has been experimenting for the past year with a 900,000-volt tube not yet perfected for demonstration. Hospitals today use a 200,000-volt tube. Five billion dollars worth of radium (20 Ib.) would be necessary to produce gamma rays equal in power to Dr. Millikan's X-rays. The entire U. S. medical profession today possesses only four million dollars worth of radium. Practical use of the Caltech apparatus has not yet been demonstrated. Before it is used on human beings, plants and animals will be subjected to the rays to test their effect on living tissue.
Olshevsky Tube. A more immediately practical development was reported from the Sloane physics laboratory, Yale University. Dr. Dimitry E. Olshevsky announced that he has constructed a tube which will enable operators to localize X-rays better. When X-rays are produced by shooting electrons at a target, they radiate in all directions from their source. Some travel through the target, others back in the direction of the bombarding electrons. Present-day tubes have utilized the rays proceeding toward the electrons' source. These rays are not so intense as those proceeding away from the electronic beam. The source of their generation is in an inaccessible position making it difficult to localize the X-rays. Dr. Olshevsky found that by using only the stronger X-rays which pass through the target and armoring the rest of the tube, he obtained a safer and more precise piece of apparatus.
Picture Tube. Also revealed at the Radiological Society meeting was the work an X-ray tube can do. Dr. George L. Clark, University of Illinois, told how he took moving pictures of molecules with the help of an X-ray tube. He used a newly developed 50,000-volt tube which makes it possible to take moving X-ray pictures. The tube acts as a powerful microscope. Rays hit the substance which Dr. Clark wished to photograph, were bent back to a fluorescent screen. When the screen was photographed the molecular changes in the substance were apparent.