I wonder what prompted Oliver Heaviside to project that a conducting layer exists in the upper atmosphere? Marconi's distance-transmissions only reached 6 km by 1896, not really using sky waves until the 1902 or 1903 demonstration of long radio distance wave propagation. Was it Heaviside's rampant intuition that simply said "a conductor ought to be up there" because of lightening occurring only for tall clouds? Or was it just a WAG? What was Kennelly's reason?