SECRETARY'S REPORT 73 



Studies on the structure of stellar atmospheres continues along 

 several lines. Dr. Owen F. Gingerich, investigating radiative equi- 

 librium, has introduced into his computer program new correctional 

 procedures developed by Dr. Krook and Dr. Eugene Avrett and is 

 preparing several manuscripts for publication. David W. Latham's 

 work on convective equilibrium will provide a basis for the theoretical 

 study of solar granulation, a subject to which Dr. Whitney's work on 

 thermal relaxation (performed with Alan Krasberg) will contribute. 

 Dr. Wliitney is also carrying out tests to determine the magnitude of 

 departures from local thermodynamic equilibrium in stellar atmos- 

 pheres; is attempting to interpret the periodicity of small-scale mo- 

 tions in terms of cepheid-like pulsation ; and has begun a new study of 

 the structure of the lunar surface by means of optical, infrared, and 

 radio data. 



During this period Miss Sylvia Boyd and Barry Goldstein com- 

 pleted measurements of the profiles of 30 absorption lines in 25 spectra 

 of pulsating variables. Robert B. Stef anik studied the time-depend- 

 ence of hydrogen excitation in a varying electron gas to determine the 

 type of atomic model necessary for obtaining realistic shock structures. 



Dr. Paul W. Hodge and Dr. Frances W. Wright have been investi- 

 gating the possible presence in the Large Magellanic Cloud of Popu- 

 lation II Cepheids, at present not known to exist there. They have 

 concentrated on the globular clusters as the most likely location, in 

 the vicinity of which previously known and new variables have been 

 studied for periods, brightness, and light-curve characteristics. 



Dr. Richard McCrosky made further progress in his observations 

 of Raman scattered Lyman a to determine the still unknown percent- 

 age of hydrogen molecules in interstellar space. He is using for this 

 purpose the infrared sensitive detectors on the Harvard College Ob- 

 servatory 61-inch telescope. 



Dr. Henri E. Mitler is making a theoretical and analytical study 

 of the possibility of optical cosmic-ray detection, on the assumption 

 that information obtained from the Cerenkov light pulse might lessen 

 the need for the usual huge counter array. He has nearly completed 

 his analysis of the probable amount of He^ produced in planetesimals 

 and its effect on concurrent element formation, the determination of 

 which is crucial for testing the cosmogonic theory of Fowler, Green- 

 stein, and Hoyle. Dr. Mitler is also investigating single-particle 

 energy levels in nuclei for possible application of the Hartree-Fock 

 theory (especially for predictability of low-lying excited states), in 

 preference to Brueckner's ^-matrix . 



Dr. Thomas W. Noonan is attempting to formulate, and then solve, 

 certain problems in cosmology and general relativity, especially in the 

 field now being studied at the Harvard College Observatory under the 

 direction of Dr. David Layzer. 



