\begin{table}%t2
%\centering
\par
\caption{Three abundance patterns examined for the lead feature.   
The abundances of $^{207}$Pb are computed for 3 assumed values of the 
production ratio $R=^{235}{\rm U}/^{238}{\rm U}$, the first 
considered as the most probable, and the other two chosen
 30 per cent below and above. All
abundances are with respect to $10^{12}$~hydrogen atoms.}
\label{isotopes}
\begin{tabular}{l|l|l|l}
\hline\hline 
$^{238}$U$_{{\rm now}}$ &  \multicolumn{3}{c}{$0.0120\pm 0.0035$} \\
$^{206}$Pb &  \multicolumn{3}{c}{$0.086\pm0.036$}\\
$^{232}$Th$_{{\rm now}}$ &\multicolumn{3}{c}{ $0.105\pm.013$ }\\
$^{208}$Pb &  \multicolumn{3}{c}{$0.099\pm0.035$}\\
\hline
    $R $     &    0.77  & 0.59  &  1.00  \\
$^{207}$Pb &   $0.075 \pm.03$  &  $0.058\pm.02$ &  $0.098\pm.04$\\
Tot. Pb &$0.26\pm0.10$  & $0.243\pm0.09$    & $0.283\pm.11$ \\
$\log(\epsilon$(Pb)) & $-0.59\pm.2$ & $-0.61\pm.2$   & $-0.55\pm.2$ \\
\hline
\end{tabular}
\end{table}