Abstract: A thermal engine employing a temperature differential to move a constant recycling fluid through a turbine. The density differential in the fluid caused by variation in temperature is used to power a turbine. The device is rotated to increase the relative difference between densities in the fluid. The engine is compactly arranged with a centrally located turbine surrounded by a heat transfer mechanism including heat transfer elements extending through the walls of the several cavities employed. A number of individual fluid cycles may be employed to increase the efficiency of the mechanism.