On the propagation of electromagnetic waves through the atmosphere
A general method of tackling the problem of the propagation of electromagnetic waves in the ionosphere has been developed and the current methods of Appleton, Hartree, Saha, Rai and Mathur, etc., have been deduced as special cases from the general results. The different assumptions by Appleton, Hartree, Bose, Booker and Rai, as regards the condition of reflexion of the waves from the ionosphere, have been shown to be identical. A symbol-correspondence chart for the different symbols used by the different workers has been given to facilitate the understanding of the parallelism between the different methods. Polarization of the radio waves have been discussed fully.
The absorption and dissociative or ionizing effect of monochromatic radiation in an atmosphere on a rotating earth
The absorption of monochromatic radiation from the sun in an atmosphere of which the density varies exponentially with height is considered; the energy of the radiation, or a definite fraction of it, is supposed to dissociate or ionize the air, and the dissociation products are supposed to recombine with one another only, and not to diffuse away from the element in which they were formed. The resulting distribution of density of the dissociation products is determined, a constant recombination coefficient being assumed, while account is taken of the variation in rate of dissociation due to the earth's rotation. The results are illustrated by numerous diagrams, showing the density of the dissociation-products as a function of height, time, latitude and season.
Report of ionosphere-investigations conducted at College-Fairbanks, Alaska, during the winter of 1933-1934
The investigations of the ionosphere begun at Fairbanks, Alaska, during the Second International Polar Year were continued during the winter of 1933–1934. Continuous automatic registrations of ionosphere virtual-heights on a frequency of 2050 kc were made. The equipment, as modified for this work, is described. The transmitter and receiver were operated at separate locations until February 10, 1934, when they were moved to College, Alaska, and further modified for side-by-side operation. 
 
A typical record is illustrated. Tabulated values of virtual height during the morning show that, following the appearance of the critical frequency, the virtual heights fall rapidly to an average value of about 210 km, identifying the layer returning reflections on this frequency as the F-layer. 
 
The periods during which reflections are returned and the times of critical frequency are shown. The usual morning increase in ionization is shown to be associated with sunrise, and from these data it is deduced that the ionizing rays of the Sun must be absorbed below a certain limit in the atmosphere when they are directed parallel to the surface of the Earth. The decrease in ionization in the afternoon is associated with time of sunset, but is not as regular. Reflections are observed most frequently near sunrise and sunset, indicating increased absorption near noon. E-layer reflections are seldom observed, and then only at night, indicating that the maximum ionization of the E-layer is not sufficient to prevent penetration on 2050 kc. 
 
Comparison of the ionosphere-data and the magnetic records at the College station is made. The magnetic disturbances usually occurred at night. There was a strong tendency for the usual morning reflections to fail to appear during or following a magnetic disturbance. A striking improvement in the character of the records with side-by-side operation is noted and records obtained under such conditions are shown.