\begin{table} %t6
\caption{\label{tab:qd}Properties of the comae of the comets: dust production rate and spectral reflectivity gradient.}
\small%\centerline
{
\begin{tabular}{lccccccc}
\hline\hline\noalign{\smallskip}
  Comet  &
 $r_{\rm h}$  &
 \multicolumn{2}{c}{Typical}  &
 \multicolumn{2}{c}{Depleted } &
 $S^\prime$ &
 Remark   \\
 & &
 $Q_{\rm H_2O}$   &  $Q_{\rm d}$  &
 $Q_{\rm H_2O}$   &  $Q_{\rm d}$  &
 (\%/k\AA)   & \\
 &   (AU)   &
  (mol~s$^{-1}$)   &  (kg~s$^{-1}$)   &
  (mol~s$^{-1}$)   &  (kg~s$^{-1}$)   & \\ 
\noalign{\smallskip}\hline 
4P/Faye            & 2.956$^O$ & -- & -- & $2.2\times10^{26}$ & 0.8 & & \\
                     & 1.604$^I$  & -- & -- & 
                                    $6.9\times10^{27}$$^*$  & 127  & & L+96 \\
                     & 1.594$^O$  & -- & -- &
                                    $6.9\times10^{27}$$^*$  & 153  & & L+96 \\
 10P/Tempel 2        & 1.669$^I$ & $1.8\times10^{27}$ &  2 & -- & -- & 
                       12.4~$\pm$~2.9 & \\
 17P/Holmes          & 3.116$^I$ & $1.4\times10^{27}$ &  4 &
                                   $4.4\times10^{26}$ &  1 & & \\
 37P/Forbes          & 2.270$^O$ & $2.6\times10^{27}$ & 11 &
                                   $8.1\times10^{26}$ &  4 & 
                       16.1~$\pm$~3.0 & \\
                     & 2.06$^I$  & 
$Q_{\rm d} = 9.81$ & & NS85 \\
 44P/Reinmuth 2      & 2.727$^I$ & $6.3\times10^{27}$ & 9 &
                                   $1.9\times10^{27}$ & 3 & & \\
 50P/Arend           & 2.374$^O$ & $4.2\times10^{27}$ & 11 & 
                                   $1.3\times10^{27}$ &  4 & 
                       9.3~$\pm$~3.3 & \\
59P/Kearns--Kwee    & 2.516$^O$ & $9.7\times10^{26}$ &  5 & -- & -- & 
                       10.5~$\pm$~2.1 & \\
                    & 2.27$^I$  &
  $Q_{\rm d} = 24.75$ & & NS85 \\
 63P/Wild 1          & 2.266$^O$ & $1.0\times10^{27}$ &  4 & 
                                   $3.1\times10^{26}$ &  1 & 
                       27.0~$\pm$~3.3 & \\
 71P/Clark           & 2.715$^I$ & $4.9\times10^{27}$ & 13 &
                                   $1.5\times10^{27}$ &  5 & & \\
 84P/Giclas          & 2.209$^O$ & $4.4\times10^{27}$ & 13 &
                                   $1.3\times10^{27}$ &  5 & & \\
106P/Schuster        & 1.666$^I$ & $7.5\times10^{27}$ & 20 &
                                   $2.3\times10^{27}$ &  8 & 
                       12.1~$\pm$~2.9 & \\
112P/Urata--Niijima  & 2.296$^I$ & $3.6\times10^{26}$ &  4 &
                                   $1.1\times10^{26}$ &  1 & & \\
114P/Wiseman--Skiff  & 1.569$^O$ & $3.1\times10^{27}$ & 17 &  
                                   $9.4\times10^{26}$ &  6 &
                       14.1~$\pm$~2.9 & \\
\hline
\end{tabular}}
\smallskip
 $r_{\rm h}$: heliocentric distance. \\
  $I$: inbound or $O$: outbound on the orbit.  \\
  $Q_{H{_2}O}, Q_{\rm d}$: water and dust production rates.  \\
  $^*$Derived from IUE measurements by Festou et~al.
(private communication).  \\
 $S^\prime [670, 792~{\rm nm}]$: normalized spectral reflectivity gradient.   \\
  L+96: \citet{lamy_etal96}.   \\
  NS85: \citet{newburn_spinrad85}.
  %\vspace*{4mm}  
\end{table}