Abstract: A machine utilizing the unbalance created by liquid driven from lower vessels to upper vessels by vapor pressure of a dual fluid said unbalance being utilized to rotate a shaft to which the vessels are attached. Continuation of rotation is achieved by a criss-cross fluid passage arrangement whereby the fluid from the lower heated vessel is transferred to the upper vessel next to be immersed in a cooling medium while the fluid from the lower colder vessel is transferred to the upper vessel next to be immersed in a heating medium.