jQuery not working

jQuery not working

<script type="text/javascript" src="../js/jquery-1.9.1.js"></script>
<script type="text/javascript" src="../js/jquery-ui.js"></script>

<script type="text/javascript">
    $('#t1').blur(function(e) {
        if (!this.value)
            {
                alert ("Enter");
            }
    });
</script>
--------------------------------------------------------------------------------------------------- html
<body>
    t1<input type="text" value="" id="t2" />
    t2<input type="text" value="" id="t1" />
    t3<input type="text" value="" id="t3" />
</body>