\begin{table}%t3
\caption{Column densities towards the \hnthic\ maximum derived using 
the LTE method. The assumed value for $T_{\rm ex}$ is $5.2^{+1.0}_{-0.6}$~K.
~~$^a$ The intensity value is for the weakest hyperfine component $F=0{-}1$ which
comprises one ninth of the total intensity of the $J=1{-}0$~line.
\label{table:columndensities}}
%\centerline
 {\begin{tabular}{llll}
\hline\hline
\noalign{\smallskip}
Molecule&$\int T{^*}{_{\rm A}}  {\rm d}v$&$N_{\rm tot}$\\
 &(${\rm K~km~s^{-1}}$)& (${\rm cm}^{-2}$)\\
\hline
\noalign{\smallskip}
\hcn$~^a$    & $0.37\pm0.03$&$(8.8\pm 1.0)\times 10^{12}$\\
\hnc$~^b$    & $1.17\pm0.03$&	                 \\
\hthicn       & $0.19\pm0.03$&$(5.2~\pm 0.1)\times 10^{11}$\\
\hnthic       & $0.52\pm0.02$&$(1.7~\pm 0.2)\times  10^{12}$\\
\hfifnc       & $0.07\pm0.01$&$(2.3~\pm 0.5)\times 10^{11}$\\
\hline
\end{tabular}}
\par
\smallskip
$^b$ A column density estimate is not given because of the obvious 
large optical thickness.  
\end{table}