Anemometers are devices which measure the velocity of the wind. The type most commonly in use today consists of three or four cups radiating from the top of a spindle; the cups catch the wind from any direction. The wind speed is either displayed on a dial at the base of the spindle or is recorded at a remote location on a clock-driven drum (anemograph). The earliest anemometers date from the 1400s and consisted of a swinging plate suspended from an axis. The plate would swing vertically in a quarter-circle across a fixed indicator as the wind would blow against it. Other types of anemometers developed were the normal-plate anemometer which used a spring-balanced plate. There was also the pressure-tube anemometer--wind blowing into the lower open end of the tube would move mercury upward in the closed end, which had indicating marks much like a thermometer. A type of anemometer employing this principle but using water was made by Dr. James Lind of England in 1776. Robert Hooke, an English scientist, developed the first practical recording anemometer with a rotating drum in 1644. It was part of a "weather clock" which also recorded the temperature, rainfall, humidity, and barometric pressure. All anemometers, old and current, share a common principle: an indicator reacting physically or electronically to a mechanical device subjected to pressure from air movement.