var $j = jQuery.noConflict();
$j(document).ready(function(){

  var one_height = $j("#box_height1").height();
  var two_height = $j("#box_height2").height();

  if (one_height > two_height)
     {
      $j("#box_height2").height(one_height);
     }
  else if (two_height > one_height)
     {
      $j("#box_height1").height(two_height);
     }
});