\begin{table}%t8
\caption{\label{ta:scale}Mean properties of high extinction complexes, clouds and clumps.}
%\centering
\par
\begin{tabular}{llrcr}
\hline\hline \noalign{\smallskip}
Size scale & Method & Mass & Radius & Vol. den.\\
 & &(${M_\odot})$& (pc) & (cm$^{-3}$)\\
\hline\noalign{\smallskip}
 complex\tablefootmark{a} & extinction & 4000 & 1.4~~ &  $6\times 10^3$\\
 clouds  & extinction & 910 & 0.7~~ & $1\times 10^4$\\
 clouds  & 1.2 mm emission \tablefootmark{b} & 700 & 0.7~~ & $9\times 10^3$\\
 clumps  & 1.2 mm emission \tablefootmark{c} & 130 & 0.15 & $2\times 10^5$ \\ 
\hline
\end{tabular}
\tablefoot {\tablefoottext{a}{The high extinction complexes should be treated as an indication since they have not so strictly defined boundaries as clouds and clumps;}
\tablefoottext{b}{smoothed maps by 20\arcsec\ Gaussian;}
\tablefoottext{c}{unsmoothed maps.}}
\end{table}