MOUNT WILSON SOLAR OBSERVATORY. 147 



(8) The components of double lines photographed In the spectra of sun- 

 spots with the 30-foot spectrograph of the tower telescope have been found to 

 be circularly polarized in opposite directions. This and much other evidence 

 indicates that sun-spots probably contain a strong magnetic field. By means 

 of spectrographic observations the areas, strengths, and polarities of these 

 fields can be measured, thus permitting a magnetic survey of the entire visible 

 hemisphere of the sun to be made. 



In addition to these investigations, much work of research described in 

 other parts of this report has been done, and the work of construction has ad- 

 vanced very satisfactorily. A spectroscopic laboratory in Pasadena, equipped 

 for investigations requiring very high temperatures and pressures, was com- 

 pleted and occupied in March. The steel building and dome on Mount Wil- 

 son for the 60-inch reflector are nearly finished, and the telescope mounting is 

 being erected on its pier. 



STAFF. 



Mr. W. S. Adams has continued his work as superintendent of the com- 

 puting division, and Mr. G. W. RItchey has had charge of construction, both 

 in Pasadena and on Mount Wilson. Dr. Arthur S. King, formerly of the 

 University of California, has been appointed superintendent of the physical 

 laboratory, and commenced work on January i. Dr. Charles E. St. John, 

 formerly Professor of Physics and Dean of Oberlin College, joined our staff 

 in May. Mr. Ferdinand EHerman has continued his work with the Snow 

 telescope. Since the completion of the Pasadena laboratory. Dr. Olmsted 

 has carried on his spectroscopic work there. Miss Louise Ware. Miss Jennie 

 B. Lasby, Miss Ruth E. Smith, and Miss Cora G. Burwell have continued 

 their study of photographs in the computing division. Miss Lillian M. Wick- 

 ham joined the staff of the computing division on February i. 



Prof. Ernest F. Nichols, Research Associate of the Carnegie Institution of 

 Washington, has been engaged in an investigation of the absorption of the 

 sun's atmosphere and in laboratory investigations on Mount Wilson during 

 the summer of 1908. Dr. Walter M. Mitchell, director of the Haverford Col- 

 lege Observatory, and Mr. H. C. Plummer, of the Oxford University Ob- 

 servatory, have also spent some time on Mount Wilson, for the purpose of 

 becoming familiar with the investigations In progress. 



The work of the Smithsonian Expedition, carried on by Mr. Abbot during 

 the summers of 1905-06, was renewed on Mount Wilson in May and is still 

 in progress. Mr. Abbot is assisted in this work by Mr. Louis B. Aldrich, of 

 the University of Wisconsin. It is a satisfaction to state that arrangements 

 have now been made by the Smithsonian Institution to construct a permanent 

 station on the mountain, where studies of the solar constant and other investi- 

 gations will be continued regularlv in the future. 



