  $SF_6$ in the vicinity of its critical point was used to study turbulent
convection up to exceptionally high Rayleigh numbers, $Ra$, (up to $5\cdot
10^{14}$) and to verify for the first time the generalized scaling laws for the
heat transport and the large scale circulation velocity as a function of $Ra$
and the Prandtl number, $Pr$, in very wide range of these parameters. The both
scaling laws obtained are consistent with theoretical predictions by B.Shraiman
and E.Siggia, Phys. Rev. {\bf A 42}, 3650 (1990).
