Sortable across columns?

Sortable across columns?


I can sort across columns but when all sortable items in a column are
moved to another column you cannot move them back to the empty
column. Any insight?
<html>
<head>
<title></title>
<script type="text/javascript" src="http://code.jquery.com/jquery-
latest.js"></script>
<script type="text/javascript" src="jquery-ui.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
    $("#container").sortable({
        items: $(".sort"),
        hoverClass: "sortHelper",
        helper: "sortHelper",
        handle: ".header"
    });
    $("#close").click(function() {
        $("#p1 .pContent").toggle();
        if ($("#p1 .closeEl").text() == "[+]") {
            $("#p1 .closeEl").text("[-]");
        } else {
            $("#p1 .closeEl").text("[+]");
        }
    });
});
</script>
<style type="text/css">
.wrap {
    width: 300px;
    float: left;
}
.sortHelper{
    border: 3px dashed #e0e0e0;
}
.sort {
    background: #eee;
    border: solid 1px #ddd;
    margin: 15px;
    width: 240px;
}
.header {
    background: #999;
    border-top: solid 1px #000;
}
</style>
</head>
<body>
<did id="container">
<div class="wrap">
    col 1
    <div id="sort1" class="sort">
        <div class="header">
            header
        </div>
        <div class="content">
            content
        </div>
    </div>
</div>
<div class="wrap">
    col 2
    <div id="sort2" class="sort">
        <div class="header">
            header
        </div>
        <div class="content">
            content
        </div>
    </div>
</div>
<div class="wrap">
    col 3
    <div id="sort3" class="sort">
        <div class="header">
            header
        </div>
        <div class="content">
            content
        </div>
    </div>
    <div id="sort4" class="sort">
        <div class="header">
            header
        </div>
        <div class="content">
            content
        </div>
    </div>
</div>
</div>
</body>
</html>