Slow scroll / crawl


I'm on Lion. My memory is vague but I know some how sometime I could get a little round disk to pop up. The further down from the disk you placed the mouse, the faster the page would scoll up. The intent was to set a slow scroll rate and sit back and read the page.

This might have been only a FF feature? Or it might have been only on older levels of Mac OS X?

My current desire is to use such a feature while reading a PDF (e.g. is it in Preview or one of the other PDF viewers?)