A similar experiment, in which a dead insect and a dead leaf were used, resulted in no ray impressions on the plates. Dr. Nodon offered as his conclusion that radioactivity is an inevitable accompaniment of living processes, and stated that the strength of photographic impressions produced in experiments such as his are an accurate measure of vitality (see _Popular Science Monthly_, October, 1924). Radium is probably present in all the planets and stars. Some time ago the Astronomer Royal of England, Dr. F. W. Dyson, demonstrated the existence of radium and of radium emanation in the sun’s chromosphere (the ocean of incandescent hydrogen gas surrounding the photosphere, or actual surface of the sun). CHAPTER II EVERYDAY USES OF RADIUM During the World War large quantities of radium were employed by the Allies for night compasses, luminous dials on airplanes, gun-sights, etc. In times of peace it is used on pendants for locating electric lights and switches in the dark, key-holes, fire-extinguishers, poison bottles, emergency call-bells, and in many other ways. For example, some mining corporations use signs in their mines made luminous in the dark by phosphorescent paint made from radioactive substances. These luminous signs are not affected by atmospheric conditions. Yet for all these uses, including “radium watches” and clocks, not more than half an ounce of radium has been used since its discovery in 1898. A few millionth parts of a gram of radium, in the form of radioactive barium sulphate, a large portion of phosphorescent zinc sulphide (crystallized zinc), mixed with varnish and some adhesive substance, give enough material to illuminate 40 or 50 watches. One gram of radium (= 16 grains) combined with 20,000 grams of secret process phosphorescent zinc sulphide is sufficient to make 667,000 watches luminous for many years. The factories of this country are now turning out about four million radium watches annually. Unless a special preparation--known only to the manufacturer--is used, the luminosity of the material gradually disappears, owing to the destruction of the zinc sulphide crystals by the powerful rays constantly bombarding them, producing flashes at the rate of 200,000 a second. The radium itself does not glow, nor does it deteriorate in power. If we examine a luminous dial through a magnifying glass, after the eyes have been in total darkness for a few minutes, tiny flashes of light may be seen. These are caused by the explosion of hundreds of millions of radium atoms. The more radium there is in the paint, the greater the number of flashes per second, and the more durable the luminosity. Since every flash means a blow upon a crystal of zinc sulphide, the crystals gradually break under the strain. In this process helium is released from the disintegrating radium atoms.