Science: Out of Thin Air

The plummeting shriek of bombs was the first warning the Germans had that there was something new over the western front. Thirty thousand feet above the battleship Gneisenau, lying camouflaged at Brest, flew U.S.-built Flying Fortresses manned by the R.A.F. They had arrived through the substratosphere, unheard and unseen in the broad daylight; they had done so because behind each of the Fortresses' four engines were turbo-superchargers, feeding them fat air to breathe in the thin heights. Though the coast below was warm and summery, the planes were frosted over with rime. They...