function slideshow(start,last,interval) {
  var frame = start;
  var nextframe = start+1;
  Effect.Appear('img1',{duration:.5,from:0.0,to:1.0});
    setInterval(function() {
    Effect.Fade('img'+frame,{duration:.5,from:1.0,to:0.0,afterFinish:function(){
    $('img'+frame).hide();
    Effect.Appear('img'+nextframe,{duration:.5,from:0.0,to:1.0});
    frame = nextframe;
    nextframe = (frame == last) ? start : nextframe+1;
    }});
 },interval);
 return;
};