JQuery UI: Horizontal Menu

I wonder how to change the layout of a JQuery UI menu from vertical to horizontal.

I have tried this but it only worked for main links on the menu bar but not the ones on the submenu.

I mean the items under 'Delphi' kept on displaying horizontally instead of dropping down vertically as these are sub items of Delphi:

<style>   
    .ui-menu:after {
        content: ".";
        display: block;
        clear: both;
        visibility: hidden;
        line-height: 0;
        height: 0;
    } 

    .ui-menu .ui-menu-item {
        display: inline-block;
        float: left;
        margin: 0;
        padding: 0;
        width: auto;
    }
</style>

                <nav>
                    <ul id="ui-menu" class="ui-menu">
                        <li><a href="#">Link one</a></li>
                        <li><a href="#">Link two</a></li>
                        <li><a href="#">Link three</a></li>
                        <li><a href="#">Link four</a></li>
                        <li>
                            <a href="#">Delphi</a>
                            <ul>
                                <li><a href="#">Ada</a></li>
                                <li><a href="#">Saarland</a></li>
                                <li><a href="#">Salzburg</a></li>
                            </ul>
                        </li>

                    </ul>
                </nav>


    $(function () {
        $("#ui-menu").menu();
    });

Edit

This is a screenshot of what I have achieved so far, and what still needs to be done:

Please let me know what I'm doing wrong.

Many thanks.

I've found this CSS NAV Generator which would solve the problem (kind of ..):

http://cssmenumaker.com/builder/1444006