The Heisler Geared Locomotives.
Left: The Heisler geared locomotive 1898
Left: Another Heisler at rest.
Left: Side elevation of a Heisler.
Left: Transverse section of a Heisler: 1898
Left: The shaft and gearing of a Heisler: 1898
Roughly 625 Heisler locos were produced, of which some 35 still exist. Eight of these are believed to be currently operational.