A temperature scale invented in 1714 by German physicist and instrument-maker Gabriel Daniel Fahrenheit (1686–1736). Fahrenheit was the first person to make practical thermometers using mercury instead of spirits of wine (alcohol). He calibrated his thermometer between two fixed points for which he used the eutectic point of salt water as 0°, which was the lowest temperature he could obtain in the laboratory, and the temperature of a healthy human which he originally called 12° and later 96°. He found that on his scale, pure ice melted at 32°F and steam at normal atmospheric pressure was 212°F. The conversion to the Celsius scale is given by: