Introduction (p. 1-14) ; Ornstein's researchers in theoretical physics (p. 15-21); Methods for measuring spectral intensities (p. 22-29); Intensities of multiplets and Zeeman-patterns (p. 30-33); The origin of spectra (p. 34-38); Band spectra (p. 39-44); The investigation of electric arcs (p. 45-53); Excitation functions and atomic diameters (p. 54-59); The Raman effect (p. 60-64); Optical investigations of isotopes (p. 65-68); Liquid cristals (p. 69-74); Technical investigations (p. 75-83); Physics of the sun (p. 84-86); List of publications (p. 87-121)