The harmonic representation of the disturbing potential

Summary The alternative harmonic representations of the disturbing potential, correct to the order of the flattening, are examined and an example is given where the incorrect use of a spherical harmonic expansion can give rise to fallacious results. The correct usage of the spherical harmonic expansion for the disturbing potential is given in the solution of the general surface integral to define the indirect effect in the case of the non-regularised geoid.