The principle of this plan of propelling vessels has been termed the "reactionary principle;" it is thus explained by the patentee.

It is well known that water contained in a vessel has a tendency to drive out the sides, or burst such vessels by pressure in every direction in proportion to the perpendicular height at which the water stands; and it is also well understood that if an opening be made at any part of the vessel, the pressure on that part will be relieved by the flowing of water therefrom, at the same time the pressure in all other directions remains the same, so long as the head of water is maintained at one water-line; and it will readily be understood, that if the vessel were free to move, and had no opposing force greater than the unbalanced internal pressure on the side of the vessel opposite, the opening would cause the vessel to move in a direction opposite-to the opening, such action resembling in principle the working of the hydraulic machine called Barker's Mill.

The mode in which this principle is to be applied to propel vessels may be thus described:a a in the figure represents a tank or cistern erected in any convenient part of the vessel, and supplied with water by a steam engine; b b is a section endways of a trunk branching from one side of the tank, and projecting over one side of the vessel at any convenient height above the water-line, a similar trunk projecting from the opposite side of the tank. Each trunk is furnished at its outer extremity with two sluice valves, the one of which (c) covers an aperture in the fore-side of the trunk, and the other (d) covers a similar aperture in the hinder or after side. Now if, both valves being shut, the tank be filled with water to any given height, the pressure upon the fore-side tending to propel the vessel forward will be as the pressure of the column of water; and supposing the pressure to be one pound per square inch, and that the sluice valves on each side are each twenty-five inches wide, then if the valves are raised one inch, the unbalanced pressure tending to urge the vessel forward will be fifty pounds.

If it be desired to give the vessel stern way, the valves d must be closed, and the valves c opened.

Busk s Hydraulic Propellers 612