Suppose a vessel 3 feet in diameter, filled with water, but another vessel, one foot in diameter, placed inside of the former, and it full of water, so as to leave 24 inches of water outside of the inner vessel,—will there not be double the amount of pressure on the outside than on the inside of the inner vessel ? An answer to this question will much oblige yours, C. W. Philadelphia, Pa., 1853. [No there will not be double the pressure on the outside that there is on the inside of the sncall vessel. Why'' Because water presses equally on all sides ; there are as many sides on the outer as on the inside of the small vessel, and just as many square inches on each side (not allowing of the difference for the construction of the box) II there was double the amount of pressure on the outer as there were on the inside, then the pressure on the square inch would be double on the outside and would be a violation of that law of hydrostatics, " the pressure is as the perpendicular height.”