  In this paper a new approach to solving the Ising-Onsager problem in external
magnetic field is investigated. The expression for free energy on one Ising
spin in external field both for the twodimensional and threedimensional Ising
model with interaction of the nearest neighbors are derived. The
representations of free energy being expressed by multidimensional integrals of
Gauss type with the appropriate dimensionality are shown. Possibility of
calculating the integrals and the critical indices on the base of the derived
representations for free energy is investigated.
