SECRETARY'S REPORT 83 



dynamics to problems of the flow of rarefied gases, various problems 

 in the dynamics of ionized gases, and the exact solution of one-di- 

 mensional problems in the kinetic theory of gases. 



Fred A. Franklin made progress in his dynamical and photomet- 

 ric studies of the rings of Saturn and of the interaction between the 

 rings and particles of the solar corpuscular stream. The results 

 should apply to other astronomical problems and should yield pre- 

 cise values of the solar corpuscular flux. 



At the Table Momitain station, Dr. Alfred G. Froiland, employ- 

 ing the atmospheric coefficients obtained by Smithsonian work, de- 

 vised a method for determining the ozone in the vertical path. 



Meteoritical studies. — The Director and Dr. Luigi G. Jacchia com- 

 pleted their analysis and discusssion of the orbits of 413 accurately 

 reduced meteors. Dr. Jacchia will continue Ms study of the reduced 

 material. 



The Director has been investigating the distribution of semimajor 

 axes among comet orbits and has derived the following law for the 

 frequency distribution of lifetimes of long-period comets: Potential 

 lifetimes of new comets are distributed according to the negative 

 three-halves power of the lifetime in number of revolutions. His theo- 

 ries on the structure of the cometary nucleus will form a chapter in a 

 forthcoming book on the solar system. From rocket, satellite, and 

 space-probe data the Director completed a study of the influx of mi- 

 crometeoritic dust on earth. The work adds significantly to knowl- 

 edge of the structure and evolution of the solar system and has prac- 

 tical importance for the engineering and operation of space vehicles. 



Kobert E. Briggs is continuing his study of the distribution of in- 

 terplanetary dust particles in space. This work should provide 

 valuable data for current and future research on the nature of inter- 

 planetary space and the origin and properties of the dust particles. 



Dr. Jolin A. Wood has been conducting a study of variations in 

 chemical composition between individual chondrules extracted from 

 a chondrite (Bjurbole). He is analyzing these small chondrules 

 with a direct- current arc emission spectrograph. He has also been 

 making a theoretical analysis of the diffusion of nickel in the nickel- 

 iron phases of iron meteorites, to determine cooling rates and ther- 

 mal histories which could account for the curious nonequilibrium 

 nickel concentration profiles noted by Ulilig and others in irons. 

 His brief analysis and description of the new meteorite Ras Tanura 

 (Saudi Arabia) is being prepared for publication. 



Dr. E. L. Fireman, Dr. David Tilles, and James DeFelice meas- 

 ured the radioactive isotopes tritium and argon-37 in recovered 

 satellite material. The tritium content of some material from the 

 Discoverer XVII satellite was unusually high but decreased rapidly 

 with increasing depth. Discoverer XVII was exposed to an intense 



