A grenade, charged with aluminium powder, barium nitrate and potassium perchlorate exploding at about 100 km altitude in the sunlit atmosphere at twilight, produced a glowing cloud which emitted the λ5535 line of BaI and the λ4554 line of BaII through photo-exdtation. The ionized barium is thought to have been produced mainly by the explosion. At an altitude of 133 km a grenade charged with aluminium powder and potassium nitrate produced a cloud which, when sunlit, emitted the λ3944 and λ3961 lines of AlI and the infra-red and violet potassium doublets, also, it is considered, through photoexcitation. A summary of the results obtained from several flights with Skylark rockets releasing grenades at night and at twilight is given. Molecular emissions and continua are discussed in following papers.