Rarified gas or plasma.
The confined vapor was passed through one of the small flexible tubes to a steel cylinder on another table, in which a vertical piston was fitted so that its upper end bore against the underside of a powerful, weighted lever. The superficial area of this piston was equal to one-half of a square inch, and it acted as a movable fulcrum placed close to the hinged end of the short arm of this lever, whose weight alone required a pressure of 1500 pounds to the square inch against the piston to lift it.
"The maximum test was made to placing an iron weight of 580 lbs. on the extreme end of the long arm of the lever. To lift this weight required a pressure of 18900 lbs. to the square inch counting the difference in the length of the two arms and the area of the piston. When Keely turned the valve-wheel leading from the receiver to the flexible tube and through it into the steel cylinder beneath the piston, simultaneously with the motion of his hand the weighted lever shot up against its stop a distance of several inches, as if the iron were cork.
"Keely then diverted the gas and fired a cannon containing a lead bullet about an inch in diameter, which went through an inch board and flattened itself to about 3 inches in diameter, with a loud report. [KEELYS SECRETS - 1888]
Figure 13.02a - Etheric Vapor HHO Generator
Figure 15.02 - Keelys Hydro-Pneumatic-Pulsating-Vacuo Engine operated with etheric vapor
Figure 5.1 - Swirling Vapor in the Atmosphere
Keelys Etheric Vapor
Keelys Vaporic Force
Original Etheric Vapor Liberator