mouse-wheel-progressive-speed

mouse-wheel-progressive-speed is a variable defined in `mwheel.el'.
Its value is

t

Documentation:
If non-nil, the faster the user moves the wheel, the faster the scrolling.
Note that this has no effect when `mouse-wheel-scroll-amount' specifies
a "near full screen" scroll or when the mouse wheel sends key instead
of button events.

You can customize this variable.