There are two lines as the following:

<div id="test"> test one jquery is a good library.<br/>
test two php is a good language.</div>
now i want to scroll them one by one (the top line hide the bottom line show.vice versa)and the line shows and hides automatically which time interval is 500 milliseconds . the scroll direction is from bottom to top.

i don't know how to do.

the following is my code. but I am totally stucked. i don't know how to write the function.

            $('#test').slideUp('500' function(){
        //how to write