Abstract
The longitudinal structure of the air shower particles in the shower disc has been investigated using the Kiel air shower array with additional fast-timing equipment. From the time delay measurements the longitudinal density distribution of particles has been derived, which near to the shower core (r<10 m) can be described by d(t)=0.39t0.9e-0.6t. This distribution proves to be similar to the longitudinal dispersion calculated for purely electromagnetic cascades.