text: In the 19th century new developments such as the discovery of photography, Rowlands invention of the concave diffraction grating, and Schumanns works on discovery of vacuum ultraviolet (fluorite for prisms and lenses, low-gelatin photographic plates and absorption of UV in air below 185 nm) made advance to shorter wavelengths very fast. At the same time Dewar observed series in alkali spectra, Hartley found constant wave-number differences, Balmer discovered a relation connecting wavelengths in the visible hydrogen spectrum, and finally Rydberg derived a formula for wave-numbers of spectral series. Meanwhile, the substantial summary of past experiments performed by Maxwell (1873), resulted in his equations of electromagnetic waves.
  In 1895, the German physicist Wilhelm Conrad Röntgen discovered and extensively studied X-rays, which were later used in X-ray spectroscopy.  One year later, in 1896, French physicist Antoine Henri Becquerel discovered radioactivity, and Dutch physicist Pieter Zeeman observed spectral lines being split by a magnetic field.
  In 1897, theoretical physicist, Joseph Larmor explained the splitting of the spectral lines in a magnetic field by the oscillation of electrons.
  Physicist, Joseph Larmor, created the first solar system model of the atom in 1897. He also postulated the proton, calling it a “positive electron.” He said the destruction of this type of atom making up matter “is an occurrence of infinitely small probability.”