The invention consists in the application of the ascensional force of air or gases developed under water to the generation of motive power, and in the combination of apparatus, by means of which the power thus produced is accumulated, transmitted and applied. The principal element of this combination is a wheel or disc (shown in plan and section, Figs. 1, 2), the dimensions of which are proportioned to the power required. On the circumference of this wheel are fixed at equal distances a given number (say sixteen) of flexible air reservoirs _a_, communicating with an equal number of tubular passages _b_, which open in the nave _c_. In the length of the fixed shaft _d_, on which this wheel is mounted, are formed two cylindrical cells E by which the air is admitted to and discharged from the flexible reservoirs _a_ by the tubular passages _b_, with which they correspond. The hydro-atmospheric wheel thus mounted and immersed to the required depth in a suitable reservoir as in _f_, is placed in communication by its hollow shaft with an air-compressing apparatus of any convenient form, which in its turn is connected with the shaft of an ordinary hydraulic wheel. The latter being set in motion acts on the forcing apparatus, by which a jet of compressed air is thrown into the hollow shaft of the hydro-atmospheric wheel by the entry cell corresponding with the orifices of the fourth quadrant or lowest immersed section of the latter. The air injected following the tubular passages within its range enters and inflates the corresponding flexible reservoirs, which thus acquiring an ascensional force proportioned to their displacing capacity and degree of immersion, carry forward the wheel in their movement towards the surface. On reaching the water line the tubular passage come into communication by the nave orifices with the discharge cell of the fixed shaft, and give egress to the air compressed in the flexible reservoirs, which collapse simultaneously with the inflation of the succeeding series by which they have in the meantime been replaced in the fourth quadrant. The latter following the ascensional movement of their predecessors give place to a third series, and collapse in the same way on passing the surface, so that each air reservoir on re-entering the water in the continued revolution of the wheel presents comparatively little resistance until it arrives at the turning point, when the communication with the entry cell of the axle being again established the movements above described are reproduced. The force thus developed by the hydro-atmospheric wheel, which represents about three times that of the prime motor, may be at this stage applied to the required transmissions of movement. When natural watercourses are not to be had within a reasonable distance of the locality in which the force is to be applied, it