<script type="text/javascript">
  fade: { speed: 300, crossfade: true};

  function carousel() {
    var i;
    var x = document.getElementsByClassName("mySlides");
    for (i = 0; i < x.length; i++) {
      x[i].style.display = "none";
    }
    slideIndex++;
    if (slideIndex > x.length) {
      slideIndex = 1;
    }
    x[slideIndex-1].style.display = "block";
    setTimeout(carousel, 4500);
  }
<\script>