Wind, indicated by a rapid rise or fall unattended by a change of temperature.
The mercury rising, and the air becoming cooler, promises fine weather; but the mercury rising, and the air becoming warmer, the weather will be changeable.
If the top of the column of mercury appears convex, or curved upwards, it is an additional proof that the mercury is rising. Expect fine weather.
If the top of the column is concave, or curved downwards, it is an additional proof that the mercury is falling. Expect bad weather.
CHAPTER XXXIII.
The thermometer is an instrument in which mercury is employed to indicate degrees of heat. Its name is derived from two Greek words, meaning heat measurer.
710. Why does mercury indicate degrees of heat?
Because it expands readily with heat, and contracts with cold; and as it passes freely through small tubes, it is the most convenient medium for indicating changes of temperature.