var album = { 
  startup: function() { 
    new PeriodicalExecuter(album.cycle, 5) // change image every 5 seconds 
  }, 
  cycle: function() { 
    new Effect.Fade('image', { // the id of the <DIV> containing the photos 
      duration: 1, 
      fps: 50, 
      afterFinish: function() { 
        new Ajax.Updater('image','/album/next', { // URL for next <IMG> tag 
          asynchronous: true, 
          onSuccess: function() { 
            new Effect.Appear('image', {
              duration: 1,
              fps: 50,
              queue:'end'
            })
          } 
        }) 
      } 
    }) 
  } 
} 
 
window.onload = album.startup

<div id="slideshow1" class="slide"><div>frame 1</div></div>
<div id="slideshow2" class="slide" style="display: none"><div>frame 2</div></div>
<div id="slideshow3" class="slide" style="display: none"><div>frame 3</div></div>
<div id="slideshow4" class="slide" style="display: none"><div>frame 4</div></div>

<script type="text/javascript">
    
    start_slideshow(1, 4, 2000);
    
    function start_slideshow(start_frame, end_frame, delay) {
        setTimeout(switch_slides(start_frame,start_frame,end_frame, delay), delay);
    }
                            
    function switch_slides(frame, start_frame, end_frame, delay) {
        return (function() {
            Effect.Fade('slideshow' + frame);
            if (frame == end_frame) { frame = start_frame; } else { frame = frame + 1; }
            setTimeout("Effect.Appear('slideshow" + frame + "');", 850);
            setTimeout(switch_slides(frame, start_frame, end_frame, delay), delay + 850);
        })
    }

</script>