  Neutrino oscillation scenarios involving large angle $\nu_{\mu} \to \nu_e$
oscillations are disfavoured in the parameter range $\Delta m^2/eV^2 >~
10^{-3}$ by recent results from the CHOOZ reactor-based $\bar{\nu}_e$
disappearance experiment. For this reason we extend our previous work on
up-down asymmetries for various oscillation scenarios by computing up-down
asymmetries and the R ratio for the entire conceivable range $10^{-4} - 10^{-1}
eV^2$ of $\Delta m^2$. Matter effects in the Earth play a crucial role. We
perform a $\chi^2$ fit to the data. We find that, because of the matter effect,
the three-flavour maximal mixing model provides a reasonable fit to
SuperKamiokande and CHOOZ data provided that the relevant $\Delta m^2$ is in
the range $4 \times 10^{-4} ~< \Delta m^2/eV^2 ~< 1.5 \times 10^{-3}$.
