How To Make This Array Work For 2 Columns

See example at: [URL]. I want the thumbnails in 2 columns, not 1. Here is the javascript:
Code:
function ImgColumn() {
var str = '';
for (var i=0; i<imgArray.length; i++) {
str += '<div onMouseOver="Enlarge('+i+')">';
my_pic = 'mypic'+i;
// my_src = imgArray[i][0];// not used here
str += '<IMG id="'+my_pic+'" SRC="'+imgArray[i][0]+'" value="'+i+'"';
str += ' alt="'+imgArray[i][1]+'" BORDER="0" HEIGHT="70" WIDTH="70"><IMG SRC="images/spacer.gif" BORDER="0" HEIGHT="1" WIDTH="10"><br>';
str += '</div>';
} return str; }

And the HTML:
Code:
<table width="200" height="400" border="0" cellpadding="0" cellspacing="0">
<tr> <td><script type="text/javascript">
document.write(ImgColumn());
</script>
</td>
</tr>
</table>