The longitude (abbreviation: Long., Î», or lambda) of a point on the Earth's surface is the angle east or west from a reference meridian to another meridian that passes through that point. All meridians are halves of great ellipses (often improperly called great circles), which converge at the north and south poles.
Use the dual thermometers to calculate relative humidity. Fisher Scientific Mason's Hygrometer has one dry thermometer and one wet thermometer which provide temperature readings for determining the relative humidity.
A hygrometer is an instrument used to measure relative humidity. It is also called a psychrometer. In order to determine relative humidity, the hygrometer makes use of wet and dry bulb thermometers. The difference in temperatures between the two measurements are an indicator of evaporation, therefore also relative humidity.