The U.S. Signal Service, a predecessor to the Weather Bureau, occupied the summit and kept records from 1870 to 1892. Starting in 1932, the current observatory began keeping records. In 1934, the observatory recorded a wind gust that at the time was the highest recorded wind speed in the world, a record that was held until 1996. The observatory's weather data have accumulated into a valuable climate record since. Temperature and humidity readings have been collected using a sling psychrometer, a simple device containing two mercury thermometers. Where most unstaffed weather stations have undergone technology upgrades, consistent use of the sling psychrometer has helped provide scientific precision to the Mount Washington climate record.