where the mind is without fear

Topics: Barometer, Weather vane, Atmospheric pressure Pages: 4 (1133 words) Published: November 21, 2013
Six's Thermometer
The thermometer on the right is a special one for recording maximum and minimum temperatures. All Six's thermometers have one long 'U' shaped tube. There are two bulbs of alcohol at the top of the tube. These cannot be seen on this thermometer. These expand or contract as the temperature changes. They then push round the indicator liquid to show the temperature. This example has no mercury, and is therefore safer. You get to see the temperature twice, it should show the same temperature on both scales. Both Celsius scales show 19 °C Six's thermometer is a registering thermometer which can record the maximum and minimum temperatures reached over a period of time, for example 24 hours. It is used to record the extremes of temperature at a location, for instance in meteorology and horticulture. It was invented by Englishman James Six in 1782; the same basic design remains in use

Mercury barometer
A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather.mercury barometer has a glass tube with a height of at least 84 cm, closed at one end, with an open mercury-filled reservoir at the base. The weight of the mercury creates a vacuum in the top of the tube. Mercury in the tube adjusts until the weight of the mercury column balances the atmospheric force exerted on the reservoir. High atmospheric pressure places more force on the reservoir, forcing mercury higher in the column. Low pressure allows the mercury to drop to a lower level in the column by lowering the force placed on the reservoir. Since higher temperature at the instrument will reduce the density of the mercury, the scale for reading the height of the mercury is adjusted to compensate for this effect. Torricelli documented that the height of the mercury in a barometer changed slightly each day and concluded that this was due to the changing pressure in the atmosphere.[1] Typically,...
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