SUMMARY
Two graphic methods of the determination of the directions of the principal moments of an isotropic plate are described in the paper. The isoclinic method utilizes the geometrical locuses of points, in which the direction of the principal moments corresponds with the direction of raster lines. It is necessary to obtain several patterns of the moire interference fringes before the complete system of isoclinics can be constructed. The method of the discreet points demands only two patterns of the moire fringes.