The Differential Gear was a large mechanical construct built by Babbage to defend the gear room of the Revolving Bridge by way of using its long blades in its front legs to attack. The Differential Gear, contrary to the "horse" that it is obviously modeled to be, does not walk, but rather, moves about by using wheels located in each of the four legs. When it moves in to attack, a large gear connected to its tail is dropped so the front legs lift up, and the blades come out to utilize a formidable slicing attack.