Geared steam locomotive
This gearing is part of the machinery within the locomotive and should not be confused with the pinion that propels a rack locomotive along the rack between the rails. The geared steam locomotives that have been built have been for conventional track, relying on the adhesion between wheels and rail.
Stephenson valve gear
American locomotives universally employed inside Stephenson valve gear placed between the frames until around 1900 when it quickly gave way to outside Walschaerts motion. In Europe, Stephenson gear could be placed either outside the driving wheels and driven by either eccentrics or return cranks or else between the frames driven from the axle through eccentrics, as was mostly the case in Great Britain.