Page:A Letter on the Subject of the Cause (1797).djvu/16

 Fire Engines. In caſes where cold Water cannot be had in plenty, the Engines may be wrought by this Force of Steam, only by diſcharging the Steam into the open Air after it has done its office.

, Where Motions round an Axis are required, I make the Steam Veſſels in form of hollow Rings or circular Channels, with proper Inlets and Outlets for the Steam, mounted on horizontal Axles like the Wheels of a Water Mill; within them are placed a Number of Valves that ſuffer any Body to go round the Channel in one Direction only: In theſe Steam Veſſels are placed Weights ſo fitted to them, as entirely to fill up a Part or Portion of their Channels, yet rendered capable of moving freely in them by the Means herein after mentioned or ſpecified. When the Steam is admitted in theſe Engines between theſe Weights and the Valves, it acts equally on both, ſo as to raiſe the Weight to one ſide of the Wheel, and, by the Re-action on the Valves ſucceſſively, to give a circular Motion to the Wheel, the Valves opening in the direction in which the Weights are preſſed, but not in the Contrary; as the Steam Veſſel moves round