  We revise the $SU(N_c)$, $N_c=3,4,6$, lattice data on pure gauge theories at
finite temperature by means of a quasi-particle approach. In particular we
focus on the relation between the quasi-particle effective mass and the order
of the deconfinement transition, the scaling of the interaction measure with
$N^2_c -1$, the role of gluon condensate, the screening mass.
