The dry-bulb thermometer measures actual air temperature and the wet-bulb thermometer measures the temperature when the air is cooled by evaporating water into it, until saturation is reached.
(the air; is cooled; T:by evaporating water into it) (the air; by evaporating; water; into it) (saturation; is reached; )
the air the air saturation
is cooled by evaporating is reached
T:by evaporating water into it
water into it