Stop double-scrolling propagation

For http://stackoverflow.com/q/16323770/1454806

HTML

<div class="Scrollable">
    <ul>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
        <li>A bunch of items to make the div scroll</li>
    </ul>
</div>
<ul>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
    <li>A bunch of text to make the body scroll</li>
</ul>

CSS

body.NoScrolling {
    overflow: hidden;
}
.Scrollable {
    max-height: 200px;
    overflow-y: scroll;
    border: 1px solid #ccc;
}

JavaScript

$('.Scrollable').on('DOMMouseScroll mousewheel', function(ev) {
	console.log('ev', ev);
  console.log('this', this);
  console.log('$this', $(this));
    var $this = $(this),
        scrollTop = this.scrollTop,
        scrollHeight = this.scrollHeight,
        height = $this.innerHeight(),
        delta = ev.originalEvent.wheelDelta,
        up = delta > 0;

    var prevent = function() {
        ev.stopPropagation();
        ev.preventDefault();
        ev.returnValue = false;
        return false;
    }
    
    if (!up && -delta > scrollHeight - height - scrollTop) {
        // Scrolling down, but this will take us past the bottom.
        $this.scrollTop(scrollHeight);
        return prevent();
    } else if (up && delta > scrollTop) {
        // Scrolling up, but this will take us past the top.
        $this.scrollTop(0);
        return prevent();
    }
});