On basis of the theorem of a universal shower development stating that a hadronically generated extensive air shower is completely described by the primary energy, the position of the shower maximum and a parameter related to the total muon number, t
he so-called correlation curve method is developed and applied to KASCADE data. Correlation information of the muon and electron content of showers measured by the KASCADE experiment are used for the reconstruction of energy and mass of primary cosmic rays. Systematic uncertainties of the method and the results are discussed in detail. It is shown that by this method general tendencies in spectrum and composition indeed can be revealed, but the absolute normalization in energy and mass scale requires much more detailed simulations.
