REPORT OP THE SECRETARY 113 



temperature conditions our observatories are in the form either of 

 tunnels in solid rock or cemented chambers under ground. In a hard 

 thundershower on January 24, 19;i0, the interior of the tunnel in 

 the mountain face was struck by lifrhtning, and the bolometer, the 

 resistance box, and other parts of the electric circuit were burned 

 out. Fortunately a second bolometer and some other spare parts 

 were in stock, so that the observer, Mr. Sordahl, by dilijjjence and 

 clever adaptations, was able to restore the circuits so as to recom- 

 mence observing with the loss of only four days. 



Mrs, Sordahl is keeping an interesting daily journal of events, 

 and, having zoological training, is also making a valuable collection 

 of the fauna and flora of the Mount Brukkaros region for the 

 United States National Museum. 



PERSONNEL 



At Washington, Dr. C. G. Abbot continues as director. Finding 

 himself unable to give sufficiently continuous attention to the work, 

 he njipointed Mr. L. B. Aldrich to be assistant director, beginning 

 May 19, 1930; F. E. Fowle, research assistant; W. H. Hoover, asso- 

 ciate research assistant (detailed to the Division of Radiation and 

 Organisms) ; Mr. A. Kramer, instrument maker; Mrs. A. M. Bond, 

 statistical assistant, reinstated October 16, 1929, vice Miss M. Mars- 

 den, resigned October 10, 1929; Mrs. M. D. (Denoyer) Johnson, com- 

 puter; Mr. W. Oliver Grant, assistant computer. 



In the field : Mr. A. F. Moore, field director. Table Mountain, 

 Calif.; Mr. F. A. Greeley, bolometric assistant. Table Mountain, 

 Calif.; Mr. H. H. Zodtner, field director, Montezuma, Chile; Mr. 

 C. P. Butler, bolometric assistant, Montezuma, Chile; Mr. L. O. 

 Sordahl, field director, Mount Brukkaros, South West Africa; Mr. 

 A. G. Froiland, bolometric assistant. Mount Brukkaros, South 

 West Africa. 



SUMMARY 



This year has been notable for both disappointment and achieve- 

 ment. Disappointment — because the high hopes of satisfactory ac- 

 curacy raised by preliminary results of reduction of observations at 

 Table Mountain proved to some extent illusory, and have given place 

 to tests of new methods designed to remove more eirectually atmos- 

 pheric sources of error. Achievement — in the invention of a new 

 method of determining the amount of atmospheric ozone, applicable 

 on every day in which solar radiation observations have been made; 

 in the discovery of tiie apparently large and exceptionally important 



