Wet the thermometer is an instrument for measuring the air humidity, is introduced as follows: when there are a lot of moisture in the air, we say that the air is wet. Scientists often use to describe how much moisture in the air relative humidity. In simple terms is to imagine the air is a towel. If you'd spilled a cup of water, you can use a towel to absorb water. But actually towels actually can absorb more than a cup of water. Maybe he can absorb five to ten cups of water. Water in some of the amount of water vapour in the air can only have part of the hydrosphere, so the relative humidity is a percentage. When the relative humidity is one hundred percent, and the air is saturated. Like a do wet towel, air can no longer take water. When the relative humidity is one hundred percent and the air is saturated, evaporation and deposition in the equilibrium state. To reach the balance again increase the amount of evaporation, as water sediment. Water vapor was called as the humidity in the air. Because of water vapor molecules so tiny so they cannot be seen, the humidity of the people has developed a creative method to measure the amount of water vapor. Anna degrees - perhaps - - - - - - - - - - - - - - - - - - A people born in Italy in the 15th century - - - - - - - - - - - - - Is the a * a came to instrument to measure the content of water vapor in the air. 。 He put a dry cotton bang on the side of a day. Then he put a is the same as the cotton of the weight of the object on the other side of the day with. When dry cotton absorbs water vapor from the air, it become more heavy and the day with the side began to sink. Is the humidity in the different between the two weight metrics.