I like to use my touchscreen to scroll.
Device Enabled (121): 1
Coordinate Transformation Matrix (123): 0.365000, 0.000000, 0.000000, 0.000000, 0.635000, 0.000000, 0.000000, 1.000000, 0.640000
Device Accel Profile (242): 0
Device Accel Constant Deceleration (243): 1.000000
Device Accel Adaptive Deceleration (244): 1.000000
Device Accel Velocity Scaling (245): 10.000000
Evdev Axis Inversion (246): 0, 0
Evdev Axis Calibration (247): <no items>
Evdev Axes Swap (248): 0
Axis Labels (249): "Abs X" (259), "Abs Y" (260)
Button Labels (250): "Button Unknown" (241), "Button Unknown" (241), "Button Unknown" (241), "Button Wheel Up" (127), "Button Wheel Down" (128)
Evdev Middle Button Emulation (251): 0
Evdev Middle Button Timeout (252): 50
Evdev Wheel Emulation (253): 1
Evdev Wheel Emulation Axes (254): 0, 0, 4, 5
Evdev Wheel Emulation Inertia (255): 10
Evdev Wheel Emulation Timeout (256): 200
Evdev Wheel Emulation Button (257): 4
Evdev Drag Lock Buttons (258): 0
The manual from www.x.org says it's the 4th button by default ... but I neither know how to gesture to scroll, nor the buttons 0,1 seem to work.