var n=136;
$("#test").click(function() {
$( this ).css( {"font-size" : n+=10});
});

<script src="http://code.jquery.com/jquery-latest.js"></script>

<span id="test">asdasd</span>
<script type="text/javascript">
var IntervalId;
$("#test").click(function() {
var n=2;
var a = $( this );
clearInterval(IntervalId);
IntervalId=setInterval(function() {a.css( {"font-size" : n+=10});},1000);
});
</script>