A beam engine is a type of steam engine where a pivoted overhead beam is used to apply the force from a vertical piston to a vertical connecting rod. This configuration, with the engine directly driving a pump, was first used by Thomas Newcomen around 1705 to remove water from mines in Cornwall. The efficiency of the engines was improved by engineers including James Watt who added a condenser, Jonathan Hornblower and Arthur Woolf who compounded the cylinders, and William McNaught (Glasgow) who devised a method of compounding an existing engine. Beam engines were first used to pump water out of mines or into canals, but could be used to pump water to supplement the flow for a waterwheel powering a mill.
The rotative beam engine is a later design of beam engine where the connecting rod drives a flywheel, by means of a crank (or, historically, by means of a sun and planet gear). These beam engines could be used to directly power the line-shafting in a mill. They also could be used to power steam ships.
These walking beams were designed by Thomas Keefer. He selected two independently-operating 70-ton Woolf Compound Rotative Beam Engines to pump Lake Ontario Water to a reservoir. The engines were built by the Dundas Iron and Brass Foundry.
The bottom part of this engine can be see in the pano http://worldwidepanorama.org/worldwidepanorama/wwp1210/html/FrancisFougere-6461.html