Quadrant barometer

112 x 13.3 x 25.4
Brass, glass, holywood and rosewood

CAT. 1878 : 253

Barometro de quadrante.

Quadrant barometer.

This quadrant barometer constructed in Lisbon by J. B. Haas, has a reservoir of mercury that communicates with two cylindrical glass tubes. One of the tubes is approximately 80 cm long and covered by three strips of wood wrapped around it like a helix. The second glass tube, approximately 7 cm long, is inside the box of the apparatus. The upper end is open, enabling a little glass cylinder to move inside it like a piston. This cylinder is suspended by a cord wound onto a little wheel joined to a horizontal axle. A second wheel mounted on this axle is wound with another cord that works the pointer of the instrument, making it move whenever the level of the mercury rises or falls. Information, although imprecise, is obtained about the atmospheric pressure. The cord that works the pointer is kept under tension by suspending two little pieces of brass from each end.

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