It should be noted that while iron is attracted by either pole of a magnet, there is such a thing as magnetic repulsion. This, however, takes place only between two magnets, and then only between like poles.
Some German physicists made a number of electrical experiments with vacuum tubes. When Sir William Crookes (England) was experimenting with similar vacuum tubes he suggested that matter was in a "radiant" state during the electric discharge within the tubes.
In 1880, H. A. Lorentz, of Amsterdam, declared that light was due to the motion of small particles revolving around the atoms of matter.
Professor Zeeman, of Holland, produced experimental proof of Lorentz's theory. He showed that the revolving "particles" were influenced by a powerful magnetic field, in the manner explained in the electron's story. This discovery was made in 1896, or sixteen years after Lorentz's declaration. It was Dr. Johnstone Stoney, of Dublin University (Ireland), who christened these particles "electrons."
The X-rays were observed for the first time by Professor Roentgen, of Germany, in 1895. The screens used for viewing the luminous effects produced by the X-rays are coated with very fine crystals of barium platinocyanide. These screens were in use for another purpose previous to the discovery of X-rays.
We know now that chemical affinity is merely electrical attraction between the atoms of matter.
The spectroscope consists of a glass prism, or series of prisms, mounted between two metal tubes. One tube is provided at one end with a vertical slit, through which the light that is to be examined is passed. At the other end of the tube is a lens, so that the beam of light from the slit emerges through the lens as a pencil of parallel rays. The pencil of light then falls upon the glass prism, striking it at an angle. In passing through the prism, the light is bent round so that it enters the second tube, which is simply a small telescope. The prism separates the æther waves according to their wave-lengths, and produces the well-known coloured spectrum, which is magnified by the telescope. The reason for the bending of the different waves is explained in the electron's story.