Land and Sea Speed Reckoner

Land and Sea Speed Reckoner



25 inches



Country of manufacture

UK and Ireland

Category: Calculating


Designed by Captain W. N. McClean July 30 1919 and constructed by  C. T. Cooper & Sons London, the rule has a logarithmic sliding scale starting at 9 seconds and ending at 3 hours and a logarithmic bottom scale starting at 0.1 mile and ending at 3 hours. This allows calculation at a constant speed of distance travelled in a given elapsed time (I think!) The front of the rule is in good condition however there is a longitudinal crack at underside about nine inches long as shown in the images. However the whole is held together with two original brass strips. An unusual slide rule nevertheless.

Captain W N McClean was a pioneer in the development of a systematic programme of river flow measurements in Great Britain

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GB Fletcher

Fletcher Wallis

Fletcher Wallis sells objects and books relating to the history of science, medicine and technology from his unit at Admiral Vernon Arcade Portobello Road. He publishes books through Vernier Press, including Antique Medicine Chests, and Corkscrew Patents from 1795. He has been dealing for thirty five years.

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