Scrolling With "Wheeled" Mice
Some mice have a "wheel" instead of a third button. You can usually click the wheel to act as either Mouse-2 or Mouse-3, depending on the setup. You can also use the wheel to scroll windows instead of using the scroll bar or keyboard commands. To do so, turn on Mouse Wheel global minor mode with the command M-x mouse-wheel-mode or by customizing the option mouse-wheel-mode. Support for the wheel depends on the system generating appropriate events for Emacs.
The variables mouse-wheel-follow-mouse and mouse-wheel-scroll-amount determine where and by how much buffers are scrolled.
