REPORT OF THE SECRETARY 99 



volume 6 of the Annals (fig. 14) and referred to in the 1944 report will 

 require some modification, since that curve did not include considera- 

 tion of sunspot effects. 



Dr. Abbot and Mr. Hoover constructed and tested a new sensitive 

 radiometer which Mr. Abbot plans to use with the aid of the Mount 

 Wilson 100-inch telescope to study the distribution of energy in the 

 spectra of stars of various types. Definite progress was made in the 

 design of the instrument, and in the control of static charges, which 

 in the past have been most troublesome. 



At the request of the United States Weather Bureau, two pyr- 

 heliometers belonging to the Bureau were repaired and recalibrated. 

 Also a silver-disk pyrheliometer was built, calibrated, and sold at 

 cost to the Bureau. 



Dr. H. Arctowski has continued his studies of the effects of solar- 

 radiation changes upon atmospheric circulation and related atmos- 

 pheric problems. A paper summarizing this work is in preparation, 



Work in the field. — Observations at the three field stations were 

 maintained in spite of the continued manpower shortage. Great 

 credit is due the directors of the stations for carrying the heavy ob- 

 serving load under difficulties. Owing to the serious illness of Mr. 

 Moore, director of the Tyrone station, that station was closed for 

 8 weeks in the spring of 1945. 



War work. — Two sets of experiments were carried out at the request 

 of the Military Planning Division, Office of the Quartermaster Gen- 

 eral, to determine the surface temperatures attained by various sam- 

 ples of military clothing under conditions similar to those of actual 

 use in the field. For this purpose we employed a special thermo- 

 electric device developed some years ago at the Observatory for the 

 measurement of skin temperatures. 



In June 1945 a contract was signed with the Office of the Quarter- 

 master General, under the terms of which the Observatory is to make 

 a detailed study of radiation received from sun and sky at Camp Lee, 

 Va., in connection with a series of tests being made at Camp Lee. 

 The preparation of instruments for this study was in progress at 

 the close of the fiscal year. 



(2) DIVISION OF RADIATION AND ORGANISMS 

 (Report prepared by Dr. Earl S. Johnston, Assistant Director of the Division) 



During the early part of the year research connected with war 

 projects was terminated. This work dealt mainly with problems of 

 deterioration of cloth, cardboard, and electrical wire insulation by 

 molds and by ultraviolet light. Contact with these projects is still 

 maintained by Dr. Johnston, who was designated liaison representa- 

 tive of the Institution with the Tropical Deterioration Steering Com- 



