The Faraday rotation has been measured in calcite parallel to the optic axis for the wavelengths λ 5893, λ 5780, λ 5461, λ 4358 and λ 4047 A. A dispersion formula for the magnetic rotation has been fitted up using the same absorption frequencies that are used in refractive dispersion. It is shown that the magneto-optic anomaly factors for the various absorption frequencies are different and the value of the anomaly factor for the absorption wavelength λ 1535, is very much lower than that for the other absorption wavelengths. (γ1535 = 0·20, γ1000 = γ500 = 0·825.) This paper also reports the values of the Verdet constant of NaClO3 for a few wavelengths from λ 5780 to λ 3650 A. A numerical error in the earlier measurements has been noticed and rectified here. In this case also a dispersion formula for magnetic rotation has been proposed and it is found that for this crystal γ1850 = 0·46 while γ900 = 0·74.