ClipArt ETC
"Get a lamp-chimney, preferably cylindrical. With a diamond or a steel glass-cutter, cut a disk of window glass a little larger than the cross-section of the lamp-chimney. Pour some fine emery powder on the disk, and rub one end of the chimney upon it, thus grinding them until they fit accurately...place [the chimney] under the water as shown. the upward pressure of the water will hold the disk in place. Pour water carefully into the tube; the disk will fall as soon as the weight of the water in the chimney plus the weight of th disk, exceeds the upward pressure of the water." -Avery 1895

Water Pressure Experiment

"Get a lamp-chimney, preferably cylindrical. With a diamond or a steel glass-cutter, cut a disk of window…