OPERATION GRAPPLE RUSHES - ROUND THREE [Allocated Title]
Rushes from round three (code name Purple Granite) of Operation Grapple, a series of tests conducted on Malden Island in 1957.
Reel one: Complete camera record of detonation filmed using a Cameflex camera. Features event in centre of frame, gradual expansion to temperature inversion, formation of cloud column and continued formation of mushroom cloud. Ends with camera looking straight up the column.
Reel two: Filmed using a Cameflex camera onboard HMS Narvik. Features column at full height and views alongside and from HMS Narvik, with cloud visible in the distance. The cloud structure is shown changing from a round top into a flat top as the winds disperse it.