Cepheid variables have long been a primary source of knowledge of galactic distances. It is therefore important to examine critically the accuracy of the cepheid distance scale to determine whether it is adequate for present needs. Proper motions resulting from the solar motion provide a fundamental determination of the distance scale, according to the well-known formula

The Princeton University Observatory carried out last summer three unmanned stratospheric balloon nights for the same purpose as that described in the preceding communication, namely to obtain high-definition photographs of the solar granulation. The special telescope for this purpose was built by the Perkin-Elmer Corporation, the electronic pointing mechanism was constructed by the Boulder Research Laboratories, and the balloons were manufactured and flown by General Mills Inc. The project was sponsored by the U.S. Office of Naval Research and by the U.S. Air Force.

The X-ray spectrum of a quiet Sun can be approximated by a 500,000° K Planckian distribution. In the absence of coronal excitation, as evidenced by the intensity of the Fe xiv green line, the X-ray spectrum has a short wave-length limit near 20 A. Coronal activity is accompanied by weak emissions down to wave-lengths as short as 6 A, which appear to be associated with coronal hot spots at temperatures of 2 x 106° K or higher.

In the U.S.S.R. the study of cosmic rays by rockets was started in 1947.

In the beginning, with the help of Geiger counters the number of charged particles was measured, and the formation of the electron-photon component in the interaction of primary particles of cosmic rays with nuclei of light elements was investigated.

In the U.S.S.R. the study of cosmic rays by rockets was started in 1947. In the beginning, with the help of Geiger counters the number of charged particles was measured, and the formation of the electron-photon component in the interaction of primary particles of cosmic rays with nuclei of light elements was investigated. It was shown that in 1947,1948,1949 and 1951 the intensity of cosmic rays at altitudes up to 75 km was the same and did not change more than by 5 %. In 1949 the data on the photon intensities outside the atmosphere were obtained. In order to measure the number of high-energy photons, one of us (A. E. Chudakov) proposed a method permitting these measurements to be made with a strong background of charged particles.

The space density and the mass distribution of meteoritic dust in the vicinity of the Earth may be directly measured using rocket and satellite vehicles. In comparison with optical and radio detection of meteors, rocket measurements are capable of detecting particles with diameters from 0.1 to 10μ. This range of particle sizes has been observed from photometric measurements of zodiacal light, by ground collections of deep-sea sediments and of the magnetic component of dust settling on flat surfaces, and collections from high-altitude aircraft. Direct measurements from rocket-launched vehicles appear the most reliable for identifying and detecting the meteoritic dust component: since meteor observations are not sensitive enough to detect this component, ground collections suffer from contamination of the terrestrial component of dust and variations resulting from hyper-velocity interactions with the atmosphere, while zodiacal light measurements are capable of determining the gross aspects of the cosmic dust in the ecliptic subject to assumptions of light scattering from solid particles.

The instruments with which we have obtained our results are displayed at the Industrial Exhibition (in Moscow), and therefore I shall not describe them here. I shall state briefly the results of those investigations in the upper atmosphere which are related to the interplanetary medium and are therefore of interest to astronomers.

We made an attempt to measure corpuscular fluxes by means of the third sputnik. For this purpose we used as indicators two fluorescent screens made of ZnS (Ag) (2 x i o - 3 g cm-2), covered with aluminium foil of different thicknesses (8 x i o - 4 g cm-2 and 4 x io~4 g cm-2). There were three aluminium diaphragms 5 mm thick in front of screens 5 cm in diameter. Each diaphragm had a window for capturing all corpuscles with a solid angle of 1/4 steradian. The emission of the fluorescent screens was detected by photo-multipliers. The electrical signals so produced were transmitted to a storage device and then to the Earth by a radio-telemetering system.

The method and results of the study of the outer ionosphere based on the ' rise' and ' set' of radio signals of the sputnik are given in full in the paper of which this is an abstract. Results of the theoretical calculations of the maximum horizontal distance rM of signalreception, which are needed for the treatment of experimental data, are also described. Calculations were carried out for a spherical Earth, and the resulting elliptic integral was tabulated by means of the high-speed electronic computer of the Academy of Sciences of the U.S.S.R. A parabolic model of the lower ionosphere and an exponential decline of electronic concentration in its outer part were accepted.

In this paper there is investigated the propagation of radio waves in a non-homogeneous ionized atmosphere with a dispersion of ionization obtained as a result of recent investigations into the structure of the ionosphere.

On the basis of the wave treatment of the problem, relations were found for the electric field intensity, expressed as Airy functions; and the results were compared with the approximate solution by geometric optics.

One of the methods used in the treatment of the results obtained during radio observations of Earth satellites consists of determining the radio-wave absorption coefficients by measurements of the electric-field strength at comparable positions.

Over the territory of the Soviet Union the Earth satellites sometimes passed below the maximum of the .F2-layer, sometimes above it, and sometimes near it.

In the preceeding reports an elegant theory of the origin of the elements has been outlined. This theory aims to be a comprehensive one. With the exception of D, Li, Be, B, the origin of all other nuclides is explained by thermonuclear reactions and subsequent neutron capture. But some difficulties arise in connexion with two groups of nuclides: the iron peak and the by-passed nuclei.