The French locomotive 1-1-1 Stephenson №6 L’Aigle from 1846 (2-2-2 by British classification).
Under the Whyte notation for the classification of steam locomotives, 2-2-2 represents the wheel arrangement of two leading wheels on one axle, two powered driving wheels on one axle, and two trailing wheels on one axle. The wheel arrangement both provided more stability and enabled a larger firebox than the earlier 0-2-2 and 2-2-0 types. This configuration was introduced in 1834 on Robert Stephenson’s ‘Patentee locomotive’.
