4-4-6-2

[1] These locomotives were perhaps the first and only attempt in North America to adapt the Mallet-compound design for passenger service, and when delivered were the world's largest passenger locos.

With a weight of 376,450 lb (170,750 kg) and 73 in (1.9 m) driving wheels, they exerted 53,000 lbf (240 kN) tractive force.

[2] But the experiment was unsuccessful: Adhesion stability was a problem, as the front engine tended to slip uncontrollably because of an imbalance of tractive effort at passenger-train speeds (this was a common problem with compound Mallets, at any speed much above walking pace).

Both locomotives were rebuilt to non-compound 4-6-2 types in 1915, retained their assigned numbers, were still in use as of 1944, and retired by 1950.

A somewhat more successful passenger Mallet design was a Russian 2-4-4-0 built between 1903 and 1909; the last examples were used into the 1950s.