'Sampling of the Stratosphere' Correspondence on Simon's idea to obtain samples of helum from the stratosphere via a rocket or balloons. Includes correspondence with Prof R Ladenburg, Palmer Physical Laboratory, Princeton University, Dr R Havens, Navy Department, Naval Research Laboratory, HC Pritchard, Chief Superintendent, Long Range Weapons Establishment, Adelaide, Australia and the Air Ministry, with descriptions of how the sampling process could work. 1948-1950