THE FIRST MOLECULAR-MODELS FOR AN ELECTROMAGNETIC THEORY OF DISPERSION AND SOME ASPECTS OF PHYSICS AT THE END OF THE 19TH-CENTURY

The first models for an electromagnetic theory of dispersion are prese nted and an attempt is made to demonstrate the important role played b y study of this phenomenon at the end of the nineteenth century. As we ll as indicating the need to have a better understanding of the micros copic properties of matter, dispersion also contributed (through the r esults obtained by Helmholtz) to the discussion over the nature of X-r ays and was fundamental for introduction of Lorentz's electron theory.