How do I determine scrollHeight?

How do I determine scrollHeight of a division use css overflow:auto?

I've tried:

$('test').scrollHeight();
$('test').height(); but that just returns the size of the div not all the content

Ultimately, I'm trying to create a chat and always have the scroll bar to the current message on the screen.

So I was thinking something like the following:

var test = $('test').height();
$('test').scrollTop(test);

Thank you,

Brian