The slide rule was a commonly used piece of equipment for making calculation for numerous occupations and scientific reasons, including meteorology. The slide rule was constructed in three basic parts, the body, slide and cursor. The body and slide were marked with scales for making calculations such as multiplication and division, with the cursor having the ability to be moved by the user to mark a specific point on the rule. In the U.K., slide rules were manufactured specifically for use by the Meteorological Office and the military between 1915 and the late 1960s when computers began to repace slide rules, according to the California State University, Long Beach. In the U.S., slide rules were not commonly used by weather or military services, apart from their use to calculate the distance of a weather balloon from the observer.
Pilot weather balloons were filled with hydrogen or helium, depending on the region in which they were used and were monitored over a 30 minute flight. Each balloon was launched equipped with a piece of equipment called a theodolite. In some balloons two of these instruments were included to record wind direction and velocity. Once the weather balloon was recovered, a meterologist using a slide rule calculated data regarding the information provided by the theodolite .
The first slide rules designed specifically for use by meteorologists were created in 1915 for the British Meteorological Office by designer J.J. Hicks. This rule contained two slides for calculating wind direction and velocity. Further improvements were made to the meteorological slide rule for the Meteorological Office, with at least six models of slide rule produced. The Meteorological Office produced the final Mk. 5 slide rule in 1968 by Blundell Harling Ltd., California State University, Long Beach reports.
Slide rules developed over their use for meteorological services, such as the standard rate of ascension by a balloon being accepted to remove one calculation that was formerly completed on a slide rule. The range of a balloon after launch was calculated using a slide rule containing extra scales and four cursors to incorporate the tail method of calculating movement and range.
