Quantum theory: Part of its history

• 1859 Bunsen-Kirchhoff: Wave length jumps (if one adds energy).
• 1885 Johann Jakob Balmer: Calculation of the ration between such wave lengths:
  2 056 410 : 1 523 310 = 1,349962 = 27:20,

  (16-4)/(16×4) : (9-4)/(9×4)

• Nils Bohr: Quantum numbers.