function slideSwitch() {
  var $active = $('#slideshow img.active');
  if ( $active.length == 0 ) $active = $('#slideshow img:last');
  var $next =  $active.next().length ? $active.next() : $('#slideshow img:first');
  $active.addClass('last-active');
  $next.css({opacity: 0.0})
    .addClass('active')
    .animate({opacity: 1.0}, 1000, function() {
      $active.removeClass('active last-active');
    });
}
$(function() {
  setInterval( "slideSwitch()", 4000 );
});