chosen $E$ in MeV, so that $\chi$ is a dimensionless variable.\
Fig. 5 represents the universality of the distributions $F_{\varphi}(\varphi;\chi, s=1)$ of the azimuth angle $\varphi$ of electrons with energies $E=22$ MeV, 70 MeV and 140 MeV and corresponding lateral distances for two values of $\chi=7.8$ and $12.5$. Curves are for one proton and one iron shower with energy $10^{17}$ eV without thinning. In Fig. 6 we show how the universality holds in the case of a young ($s=0.7$) and an old ($s=1.3$) shower, this time taking electron distributions for one $10^{19}$ eV proton shower and ten $10^{17}$ eV iron showers with thinning procedure switched on. The energies and lateral distances refer to $\chi=12.5$. Fig. 5 and 6 also demonstrate the universal behaviour of $F_{\varphi} (\varphi ; \chi, s )$ with respect to the change of the primary particle energy or mass.

Variable $\xi$
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It is not only that the distributions $F_{\varphi} (\varphi ; \chi, s )$ are universal but also the distributions of the polar angle $\theta$ show a similar character. We have searched for *one* variable which could combine the energy, lateral distance and $\theta$ angle for constant $\varphi$ and $s$. We have found a variable $\xi$ 