10 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1951 



The archival material of the Bureau was enriched by the addition 

 of the original catalog (in Powell's handwriting) of the photographic 

 negatives made on Maj. John W. Powell's famous expedition down 

 the Grand Canyon of the Colorado. 



Intcimationul Exchange Sei'vice. — As the official agency for the ex- 

 change with other countries of governmental, scientific, and literary 

 publications, the Exchange Service handled 1,011,000 packages of 

 sucli publications (total weight, 788,773 pounds) for transmission, 

 or about the same as during the previous year. As last year, no ship- 

 ments were made to China or Rumania, but consignments are moving 

 to all other countries. The number of sets of United States official 

 publications sent abroad in exchange for similar publications of other 

 countries is now 102 (61 full and 41 partial sets). Eighty-five copies 

 of the Federal Register and 92 of the Congressional Record are also 

 sent abroad through the Exchange Service. 



National Zoological Park. — This year brought the largest attend- 

 ance in the history of the Zoo — an estimated total of 3,460,400 visitors, 

 or at the average rate of more than 9,000 a day. At the close of the 

 fiscal year, there were 2,813 animals in the Zoo collections, the ad- 

 ditions during the year (1,768) almost exactly balancing the losses 

 and removals (1,776) . Among the more unusual accessions, some rep- 

 resenting species never before shown in this Zoo, were 17 Santa Marta 

 tinamous from Colombia; a splendid example of the black-headed 

 python of Australia ; a rare native wild goat from Crete ; specimens 

 of the large Meller's chameleon from Africa ; three-banded armadillos 

 from central South America; and six Labrador lemmings. In all, 

 217 creatures were born or hatched at the Zoo — 62 mammals, 57 birds, 

 and 98 reptiles. 



Astrophysical Observatory. — The Observatory continued its studies 

 of solar radiation at its two high-altitude field stations at Table Moun- 

 tain, Calif., and Montezuma, Chile. At Table Mountain a method is 

 being developed for determining by spectrobolometric measurements 

 the quantity of ozone in the upper atmosphere. The textile-exposure 

 studies at the Montezuma station for the Office of the Quartermaster 

 General were terminated in May. In cooperation with the Meteorolog- 

 ical Division, Chemical Corps, at Camp Detrick, Md., some work was 

 done on the problem of improving the melikeron, an instrument de- 

 veloped some years ago by the Observatory to measure outgoing ra- 

 diation from earth to space. Two silver-disk pyrheliometers were 

 constructed and furnished at cost, one to the Government of Israel 

 and the other to the Air Force's Research Laboratories at Cambridge, 

 Mass. The division of radiation and organisms, following a 2-year 

 period of setting up specialized equipment and facilities, and new 

 electronic instruments, has begun a series of biochemical investiga- 



