By 'continue scrolling', do you mean if you scroll fast and leave go the scrolling slows down gradually then stops, as opposed to stopping immediately?
If so, that's called 'inertia'. I don't have Lion, but in Snow Leopard that feature is in the Trackpad pane in System Preferences; look for Scroll (and select "with inertia" from the popup). Hopefully, that's also there in Lion!