Correspondence from W.R. Piggott to Edward Appleton, 1941-1944

Correspondence from W.R. Piggott to Edward Appleton, dated 1941-1944. The material includes a letter from L.W. Hayes on the accuracy of Delhi ionosphere measurements, dated 1943, and 'Note on the organisation of ionosphere recording stations after the war', dated 1944 prepared by Piggott for the Royal Society. The Delhi measurements drew Appleton's attention to the geomagnetic anomaly which became a focus for his later research. See Clark, Sir Edward Appleton, page 151.