The dynamical equations which govern the simultaneous flows of heat and electricity in crystals express the electric and heat current densities as linear combinations of the gradients of the electrochemical potential and the temperature. When a magnetic field is applied, the coefficients in these equations become functions of the applied field. Magnetic field effects are included by expanding the coefficients in powers of the magnetic field. For isotropic media, expansion of the electrical and thermal conductivities and the Seebeck coefficient to the first order in the magnetic field gives the Hall, Righi‐Leduc, and Nernst coefficients, respectively. The resulting dynamical equations have been solved assuming (a)&rgr;,&kgr;,Sare not functions of position or temperature,H≠0, current densityJis either parallel or perpendicular to the temperature gradient ▿Tand to the heat current densityQ; (b)&rgr;and&kgr;not functions of position or temperature,H=0,J∥▿T.