Gold Visibility Meter Mk11
This wonderful instrument was invented by Captain Ernest Gold who was was General Haig's 'weather man' in WW1. He served with the RFC, who in 1915 were the only people really interested in meteorology. He was a brilliant graduate and rose to very senior posts between the wars. His 'Gold Visibility Meter', was used for making the accurate assessment of visibility on airfields at night feasible for the first time. The device was operated by Met Office staff where there were often two visibility lights mounted at the far end of the runway. These carried very high quality incandescent bulbs of a known candle power. The Visibility Meter consisted of a graduated glass slide ranging from completely clear to completely black. Each Observer routinely calibrates them on nights of very good visibility. This is done by drawing the slide across the viewing field until the Vis Light is just extinguished. On a night of poor vis the point at which the light then extinguishes gives an indication of the opacity of the atmosphere between the observer and the Vis Light and the Met officer could recommend if conditions were good enough for flying. Our instrument comes complete in its Bakelite storage box and carries serial number 1487/43 dating it to 1943 and was manufactured by Casella of London. It is complete with rubber eye piece in good condition and the often missing extension tube for the reverse side. Transit case measures 11” x 3.5” (28 cm x 9 cm.)These instruments were only declared obsolete in 1966.