Notes on the use of aneroid barometers in the gold coast

For several years it had been realized that aneroids in the Gold Coast showed a distinct lag in the readings when subject to fairly large changes of height. The range of height in the Colony, however, being relatively small and control heights fairly numerous, little interest was taken in the cause, which was generally thought to be due to hysteresis. * All aneroids in use on the Gold Coast are graduated on Airy's scale which is based on latitude 45° and temperature 50° F. In 1921 Mr. C. L. T. Griffith, at that time Chief Instructor of the Survey School, carried out various tests with a number of aneroids, and from these tests concluded that the main source of error arose from inappropriate graduation of the height-scale relative to pressure; using as constants latitude 15°, temperature 86° F., and mean humidity 67 per cent., he worked out a proposed general scale for the Tropics. Ten years later the purchase for test purposes of new aneroids graduated to this scale was considered but was eventually postponed when it was learnt that the question of a special scale for use in the Tropics was under consideration at home by a special Committee consisting of representatives of the Admiralty, War Office, Air Ministry, and National Physical Laboratory.