JQuery :: Slide One Div Out Left While Sliding One In Right?

I have a container div with two inner divs. I have one inner div visible taking up 100% of the visible area and another hidden div. I
want the visible div to slide to the left while simultaneously sliding the other div in from the right. This works fine except that while the right div is sliding in, it appears below the left div. How can this be done?

Here is the code:

<script type="text/javascript" src="js/jQuery/jquery.js"></script>
<script type="text/javascript" src="js/jQuery/effects.core.js"></
script>

[code]....