Properties of the Wehnelt cathode rays

The discharge of electricity through gases is a subject that has had a most wonderful growth, — a growth possibly greater than that of any other single division in physics. With the discovery of cathode rays, X-rays, radioactivity, and rays of positive electricity, a new era was begun. The cathode rays were the first of the above to be brought to our attention, however, but little was known of their properties until the researches of the last decade. About fifteen years ago the wonderful X- or Roentgen rays were discovered. A few years later came that almost revolutionizing discovery of radioactivity, — revolutionizing because we are obliged to change our conceptions regarding the molecule and atom. Another of equal importance because of its bearing upon chemical composition, is afforded by J. J. Thomson´s recent investigations on rays of positive electricity.