REPORT OF THE PRESIDENT, 1923. 5 



of sun-spots in both northern and southern hemispheres of the sun is 

 reversed in the spots of the new cycle coming in; and in still another 

 field includes the securing of definite evidence regarding the internal 

 motions of the great spiral nebulae which are among the most interest- 

 ing objects in the heavens. 



Turning from the work of Mount Wilson Observatory, which looks 

 out over the surrounding universe, we find the Geophysical Laboratory 



p , . - attaining comparable success in its attack upon the 



Geophysical difficult problems concerning that little-known realm 

 a oratory. represented by the interior of the earth. Here the 

 most fundamental researches in physics and chemistry are brought to 

 bear in an effort to secure evidence regarding conditions prevailing in a 

 region for which immediate visual exploration is impossible. As in 

 the study of the sun at Mount Wilson, we have in this Laboratory a 

 series of experiments under way for the purpose of developing for 

 immediate research purposes a group of conditions similar to those 

 existing in the special region being examined, which in this case is 

 the interior of the earth. The results of this work in the past year are 

 embraced in many publications touching, on the one hand, the most 

 intimate problems of atomic structure of minerals or elements con- 

 cerned in the physical or chemical processes investigated ; they extend, 

 on the other hand, to a study of materials emanating from the 

 interior of the earth, as in examination of the lavas of the Hawaiian 

 Islands, and the chemical investigation of fumaroles of the Katmai 

 region of Alaska. 



The student of the interior of the earth does not have advantage of 

 the phenomena based on light transmission, such as enable the astron- 

 omer to view changes in progress on the sun and stars; but, not to be 

 denied an immediate living touch with the field of his investigations, 

 the geophysicist avails himself of other types of vibration, and through 

 the study of earthquake waves and by other means becomes in some 

 measure aware of present conditions in the earth's interior. 



Inasmuch as earlier reports have directed attention to a cooperative 



research of unusual character aimed toward solution of certain 



critical problems in earthquake study, it is appro- 



in'^SgatSn P^iate at this time to note that a very large measure 



of progress has been realized in these investigations 



within the last year. The report of activities presented in the Year 



Book by Dr. Arthur L. Day, chairman of the committee, is an 



extremely interesting story. 



