\begin{table}%t4
\caption{ Parameters of the colour gradients distributions. \label{tab4}}
%\centerline
{\begin{tabular}{llllllll}
\hline \hline 
 Grad.        & $N$  &Min  &Max  & Mean  &$\sigma$& \multicolumn{1}{c}{Skew} &$\sigma_{\rm err}$ \\ 
 \hline
 $\Delta_{UB}$& 41 &--0.08&--0.25&--0.157 & .042& --$0.52\pm .6$& .027 \\  
 $\Delta_{BV}$& 53 &--0.02&--0.12&--0.066 & .022& --$0.32\pm .5$& .013 \\  
 $\Delta_{BR}$& 43 &--0.03&--0.13&--0.082 & .028& --$0.27\pm .6$& .015 \\ 
 $\Delta_{VI}$& 47 &--0.03&--0.16&--0.061 & .036& --$1.12\pm .6$& .021 \\  
 $\Delta_{VJ}$& 53 &--0.01&--0.35&--0.136 & .092& --$1.15\pm .5$& .032 \\  
 $\Delta_{VK}$& 53 &--0.07&--0.52&--0.227 & .112& --$1.48\pm .5$& .035 \\  
 $\Delta_{JH}$& 54 &--0.01&--0.11&--0.054 & .026& --$0.51\pm .5$& .017 \\  
 $\Delta_{JK}$& 54 &--0.04&--0.17&--0.093 & .033& --$0.51\pm .5$& .017 \\ 
\hline
\end{tabular}}
\par
\smallskip
(1) Gradient 
$\Delta_{AB}$ of colour $A-B$. (2) Number $N$ of objects. (3)~Minimum (one value in 
$V-I$ rejected). (4) Maximum. 
Both are averages of two extreme values (NGC~5866 rejected). (5) Mean.  
(6)~Standard deviation $\sigma$. (7) Skewness and its probable error from the formula 
in {\em Numerical Recipes} (Press et~al.  1992). (8) Probable errors of measured
gradients $\sigma_{\rm err}$. No rejections are made for the calculation of the parameters 
in Cols.~(5)--(7).    
\end{table}