  A classification of the $IJ^{PC}=00^{++}$ mesons is performed on the basis of
the K-matrix analysis of meson spectra in the reactions: (i) GAMS data on $\pi
p\to \pi^0\pi^0 n$, $\eta\eta n$, $\eta\eta' n$; (ii) Crystal Barrel data on
$p\bar p~(at~rest)\to \pi^0\pi^0\pi^0$, $\pi^0\pi^0\eta$, $\pi^0\eta\eta$;
(iii) CERN-M\"unich data on $\pi p\to \pi^+\pi^- n$; (iiii) BNL data on $\pi
N\to K\bar K N$. The analysis points to the existence of four comparatively
narrow scalar resonances which correspond to the following poles of the
scattering amplitude (in MeV): $(1015\pm 15)- i(43\pm 8)$, $(1300\pm
20)-i(120\pm 20)$, $(1499\pm 8)-i(65\pm 10)$ and $(1780\pm 30)-i(125\pm 70)$.
The scattering amplitude also has a fifth pole $f_0(1530^{+90}_{-250})$ at the
complex mass $(1530^{+90}_{-250}) - i(560\pm 140)$. The masses of the K-matrix
poles (bare states) are at $720\pm 100$ MeV, $1230\pm 50$ MeV, $1260\pm 30$
MeV, $1600\pm 50$ MeV and $1810\pm 30$ MeV. The quark content of the bare
states is analyzed using the values of their couplings to the $\pi\pi$, $K\bar
K$, $\eta\eta$ and $\eta\eta'$. It is shown that one of the bare states in the
mass region 1200-1600 MeV is superfluous for the $q\bar q$ classification and
should be considered as the lightest glueball.
