ISOTHERMAL SURFACES IN E(3) AS SOLITON SURFACES

We show that the theory of isothermic surfaces in E(3) - one of the ol dest branches of differential geometry - can be reformulated within th e modern theory of completely integrable (soliton) systems. This enabl es one to study the geometry of isothermic surfaces in E(3) by means o f powerful spectral methods available in the soliton theory. Also the associated non-linear system is interesting in itself since it display s some unconventional soliton features and, physically, could be appli ed in the theory of infinitesimal deformations of membranes.