10 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 50 



in New Mexico. In all, 123 creatures were born or hatched at the 

 Zoo — 60 mammals, 17 birds, and 46 reptiles. Both pairs of the Zoo's 

 hybrid bears (female Alaska brown X male polar) produced cubs. 

 The number of visitors to the Zoo reached the all-time record of 

 3,437,669, which was 91,619 more than last year. Groups from 

 schools numbered 1,973, aggregating 102,553 individuals, and came 

 from 31 States, some as far away as Maine, Florida, Washington, 

 California, and New Mexico. 



Astrophysical Observatory. — Late in the year the Director, L. B. 

 Aldrich, made an inspection trip to the two solar-radiation field sta- 

 tions now operated by the Astrophysical Observatory, one at Table 

 Mountain, Calif., and the other at Montezuma, Chile, and was able 

 to make valuable intercomparisons of methods and results of the 

 research. A significant increase of one-fourth of 1 percent in the 

 radiation emitted by the sun in the two decades from 1925 to 1944 

 has been calculated from the solar-constant determinations at the 

 Chilean station. The Observatory's work at the temporary observing 

 station at Miami, Fla., for the office of the Quartermaster General, in 

 connection wath studies of fabric resistance to solar radiation, were 

 terminated there, and the special equipment was moved to the Table 

 Mountain, Calif., station. Three silver-disk pyrheliometers were con- 

 structed under the supervision of W. H. Hoover and furnished at cost 

 to institutions in New Zealand, Venezuela, and Rumania, and two 

 modified Angstrom pyrheliometers and one special water-vapor 

 spectroscope were furnished to a meteorological institute in Belgium. 

 The Division of Radiation and Organisms concluded its reorganization 

 and reconstruction of the facilities of its laboratories, which are now 

 equipped with four constant-temperature rooms and with new types 

 of modern instruments and are in first-class condition for photo- 

 chemical research on plants. Several new lines of research are being 

 inaugurated. The sixth edition of the Smithsonian Meteorological 

 Tables, compiled by Robert J. List, of the United States Weather 

 Bureau, was in press at the close of the year; and the manuscript of 

 the ninth edition of the Physical Tables was nearly completed under 

 the direction of Dr. William E. Forsythe, physicist, of Cleveland, 

 Ohio. 



National Air Museum. — The report to Congress on the National 

 Air Museum, required by law, was submitted on March 17, 1950, 

 making recommendations for the acquisition of suitable lands and 

 buildings for the museum. The Advisory Board met on May 24 and 

 gave considerable attention to this report and to the problems involved 

 in advancing the Air Museum's site-procurement and building pro- 

 grams. Several outstanding accessions to the collections were re- 

 ceived, including the B-29 superfort Enola Gay, the first aircraft to 



