滚动到div的底部？

I am creating a chat using ajax requests in rails and I'm trying to get a div to scroll to the bottom without much luck.

I am wrapping everything in this div:

#scroll {
    height:400px;
    overflow:scroll;
}

Is there a way to keep it scrolled to the bottom by default using JS?

Is there a way to keep it scrolled to the bottom after an ajax request?