Event.observe(window, 'load', function() {
  $$('.slideshow').each(function (el) {
    i = 100;
    el.getElementsBySelector('img').each(function (img) {
       img.hide();
       img.style.zIndex = i;
       img.origIndex = i;
       i++;
    });
    new Effect.Appear(el.getElementsBySelector('img').first(), {duration: 2.0, from: 0, to: 1 });
    el.getElementsBySelector('img').first().addClassName('active');
    new PeriodicalExecuter(function (pe) {
      nextSlide(el);
    }, 5);
  });
});

nextSlide = function (el) {
  active = el.getElementsBySelector('img.active').first();
  next = active.next();
  if (!next) next = el.getElementsBySelector('img').first();
  next.hide();
  active.style.zIndex = active.origIndex;
  next.style.zIndex = 1000;
  new Effect.Appear(next, {duration: 2.0, from: 0, to: 1});
  active.removeClassName('active');
  next.addClassName('active');
}