She was a frigate of great speed, fitted with
high-pressure engines which admitted a pressure of seven atmospheres.
In 1955, Lanz equipped the Bulldog with a full-diesel (or
high-pressure engine), although it was still a 1-cylinder, installed horizontally, and Lanz needed help.
A
high-pressure engine was simpler than the old models, and more dangerous.
While Watt is credited with inventing the low-pressure steam engine, Oliver Evans built the first
high-pressure engine.
In 1815, the Fairmount Water Works opened, powered by a Boulton and Watt condensing steam engine and a
high-pressure engine designed by Oliver Evans.
(Oliver Evans's
high-pressure engine drove some sawmills in Pennsylvania.)