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o the other, and the stop-cock at c be turned so as to establish a communication between them, it will be found that an inch of mercury in one limb will balance 13 1/2 inches of water in the other, showing the relative specific gravities of the two fluids to be as 13 1/2 to one.
（Meteorology.) An instrument by which the variations of atmospheric pressure are automatically recorded on a sheet of paper.
Napier's instrument, patented in 1848, is intended to mark the variations of atmospheric pressure during an entire period of 24 hours. Connected with the barometer-tube is a vertical spindle carrying a card which has on its surface a number of radial lines and concentric circles; the radial lines represent fractions of inches, and the concentric circles represent portions of time.
Above the card is a lever carrying a vertical pricker, which is made to rise and fall at certain regular intervals of time, and to travel from the inn