  A correlation is obtained for the drag coefficient $c '_f$ of the turbulent
boundary layer as a function of the effective boundary layer Reynolds number
$Re$ that we previously introduced. A comparison is performed also with another
correlation for the drag coefficient as a function of the traditional Reynolds
number $Re_{\th}$, based on the momentum thickness of the boundary layer
proposed recently by R.D.Watson, R.M.Hall and J.B.Anders (NASA Langley Research
Center) on the basis of different set of experimental data. We show that the
correlation obtained by us agrees with experimental data from the Illinois
Institute of Technology, but is incompatible with the data obtained in the
Royal Institute of Technology at Stockholm. On the other hand, both sets of
data are in disagreement with the Langley correlation.
