Image of incendiary socks dropped from free flying balloons. Detail from: Civil Defence Training Pamphlet No 2: Objects Dropped From The Air (3rd Edition). Issued by the Ministry of Home Security. This training pamphlet described some of the objects which could be found on the ground after and air-raid, including certain items which, though not of enemy origin, may be mistaken for hostile weapons, and others that may drop from the air at any time.