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Home > All Images > 2002 > July > 25 Jul 2002

Images Dated 25th July 2002

Available as Framed Photos, Photos, Wall Art and Gift Items

Choose from 23 pictures in our Images Dated 25th July 2002 collection for your Wall Art or Photo Gift. Popular choices include Framed Photos, Canvas Prints, Posters and Jigsaw Puzzles. All professionally made for quick delivery.

Drawing of Robert Hookes wheel barometer of 1665 Featured 25 Jul 2002 Print

Drawing of Robert Hookes wheel barometer of 1665

Wheel barometer. Drawing of a wheel barometer in Micrographia (1665) written by the British physicist Robert Hooke (1635-1703). The barometer was used to measure air pressure. Mercury filled a glass tube (at centre) which is open at one end (marked F') and has a sealed bulb (at centre top) at the other. In the bulb a vacuum provides enough suction to prevent the mercury from flowing out of the tube. The open end of the tube contains a ball which floats on the mercury. The float is attached to the pointer by a length of string. If air pressure rises the mercury is forced up into the bulb and the level of the mercury at the open end drops. As the float drops too, the pointer moves