  Evidence for a positive cosmological constant $\Lambda$, derived from the
Ly$\alpha$-forest in high-resolution spectra of quasars, leads to a closed,
low-density, $\Lambda$-dominated universe. The analysis is based on the
assumption of a universal shell structure expanding predominantly with the
Hubble flow. Supporting evidence comes from two pairs of very wide absorption
lines in the spectra of two quasars separated by 8 arcmin on the sky. These
results contradict the higher values of the density parameter $\Omega_{M,0}$
derived, for example, from clusters of galaxies by the pure gravitational
instability theory. Implications thereof and for the amount of non-baryonic
dark matter in the universe are discussed with some $\Lambda$-dominated models,
in particular with $\Omega_{M,0} = 0.2$ and with pure baryonic models. The
evidence points to low-density, closed models with spherical metric, expanding
forever.
