This device used two large pulleys turning two small pulleys to increase the rotational speed of a stimulus wheel beyond what could be achieved by direct hand rotation. The two axle color mixing apparatus could achieve much higher speeds than the single axle version. Wheels with different combinations of colors were used to demonstrate the principles of color mixing. Wheels with black and white patterns were used to demonstrate motion aftereffects and to produce colors using Bentham's patterns. It was manufactured by Milton Bradley Co., Springfield Mass., and was patented Feb 28, 1893.