Water evaporates from the cloth, causing the temperatures on that thermometer to be lower the the other. A RAIN GAUGE measures the amount of rain that has fallen over a specific time period. A WIND VANE is an instrument that determines the direction from which the wind is blowing. An ANEMOMETER measures wind speed.

An instrument that measures air pressure is called a barometer. One of the first barometers was developed in the 1600s. The original instrument had mercury in the small basin, with an upside down glass tube placed in the mercury. The height of mercury in the glass tube could be measured in inches.

A RAIN GAUGE measures the amount of rain that has fallen over a specific time period. A WIND VANE is an instrument that determines the direction from which the wind is blowing. An ANEMOMETER measures wind speed. The cups catch the wind, turning a dial attached to the instrument.