118 ANNUAT^ KEPOKT SMITHSONIAN INSTITUTION, 192 8 



brass support, rotatable in a ground joint, the radiometer could be 

 inclosed in an airtight outside case of brass having windows, toward 

 which the radiometer could at any time be made to look out by merely 

 rotating the brass piece in its well-ground seat. 



With this simple but adequate apparatus the Mount Wilson expe- 

 dition was renewed by the writer in 1928, with a high degree of suc- 

 cess, which must be related in next year's report. 



Personnel.— During the year the personnel has been as follows : 



At. Washington : 



Director, Dr. C. G. Abbot. 



Research assistants, F. E. Fowle, Jr., L. B. Axdrich. 



Temporary assistant, M. K. Baughman. 



Computers. Mrs. A. M. Bond, Miss M. A. Mausden. 



Instrument maker, A. Krametr. 

 At Table Mountain : 



Field director, A. F. Moore. 



Field assistants, H. H. Zodtner, H. B. Frhieman.' 

 At Mount Montezuma : 



Field directors, H. B. Fre:eman, H. H. Zodtner. 



Field assistants, E. E. Warner, M. K. Baughman. 

 At Mount Brukkaros: 



Field director, W. H. Hoover. 



Field assistant, F. A. Greelett. 



Summary. — A novel research on the relative cooling of the human 

 body by radiation and by air convection has yielded unexpected and 

 valuable results. Improvements in instruments include a new form 

 of sensitive radiometer in which by the substitution of hydrogen for 

 air a great increase in quickness of response permits the use of exces- 

 sively light systems and promises a great development of sensitive- 

 ness. Continued progress in the reduction and systematization of 

 the results of solar radiation work ha^e brought the study of the 

 ozone content of the atmosphere as a new element in the determina- 

 tion of the solar constant of radiation. Daily observations have been 

 continued at Table Mountain, Calif., Mount Montezuma, Chile, and 

 (in cooperation with the National Geographic Society) at Mount 

 Brukkaros, South West Africa. By cooperation with the United 

 States Weather Bureau, daily publication of the values of the solar 

 constant of radiation for the use of meteorologists has been effected. 



C. G. Abbot, 

 Director.^ Astrophysical Observatory. [ 



The Secretary, , 



The Smithsonian Institution. 



* Mr. Freeman assisted for a short time after bis return from South America, pending 

 other assignment. 



I 



