The propagation of long waves at great distances has been studied in great detail by Austin, by Round, Eckersley, Tremellen, and Lunnon, by Espenschied, Anderson, and Bailey, and by Yokoyama and Nakai. Thus the propagational characteristics of long waves, considered merely as channels of communication, are well known. There have remained, however, a number of unexplained directional effects of which one might quote as an example the difficulty, noticed by Round, Eckersley, Tremellen, and Lunnon, of receiving signals whose great circle path traversed the earth’s magnetic poles. Pronounced directional effects at short distances have been reported by Naismith. He found that the intensity of the space wave from GKB, Northolt, was approximately twice as great at Manchester as at Exeter although both receiving points are at the same distance from the transmitter. At Manchester the receiver was north of the sender, while at Exeter the direction was west.
On the rotation of the plane of polarization of long radio waves