SECRETARY'S REPORT 67 



inating the errors arising from atmospheric opacity. On the other 

 hand, the measurements of atmospheric opacity in the observing pro- 

 gram of the Astrophysical Observatory have become of increasing in- 

 terest to meteorologists and geophysicists in recent years. Records 

 from Table Mountain show clearly the increased opacity of the atmos- 

 phere arising from the Alaskan volcano in 1953. However, they show 

 no effect of increased opacity arising from the explosions of nuclear 

 or thermal nuclear bombs. 



Meteoritic studies. — Meteoritic studies have been a part of the 

 Smithsonian Institution's scientific research program for the past 80 

 years. The Institution's meteorite collection, which has been de- 

 veloped through these decades of exploration and study, is one of the 

 most outstanding in the world. In cooperation with meteorite spe- 

 cialists in the department of geology of the United States National 

 Museum, E. P. Henderson and the late Dr. W. F. Foshag, a freshly 

 oriented plan of meteoritic research has been explored. This new 

 program has been placed under the supervision of Dr. John S. Rine- 

 hart for the purpose of ascertaining the answers to numerous questions 

 concerning astrophysical dynamics. As a result, the following aspects 

 of the problem are now in course of consideration : Past and current 

 research pertaining to the nature and distribution of meteorite debris 

 and micrometeorites ; the nature of meteorite craters; exterior and 

 terminal ballistics and other phenomena that relate to meteoritic im- 

 pact against the earth ; and the extraterrestrial life of meteorites. All 

 these studies are directed toward answering astrophysical rather than 

 specific geologic questions. 



Under the sponsorship of the United States Air Force, the Astro- 

 physical Observatory has initiated a program whose objective is to 

 develop a better understanding of the processes that cause ablation as 

 meteorites hurtle through the atmosphere. Effort thus far has been 

 confined (1) to renewed search of museum collections for specimens 

 that exhibit ablation, and (2) to a metallurgical examination of me- 

 teorites that show heat alteration effects caused by their passage 

 through the atmosphere. 



In June 1956, Dr. J. S. Rinehart, Nicholas Matalas, R. O'Neil, and 

 R. Olson journeyed to the meteorite crater near Winslow, Ariz., in 

 order to investigate, by systematic sampling, miniscule spherules, 

 globules, and pieces of meteoritic matter in the soil around the crater. 

 The search will extend over an area of more than 100 square miles. 

 Magnetic means are being used to extract meteoritic material from 

 soil samples. Initial effort is being directed toward the development 

 of sampling techniques and the identification of material. The results 

 of the first survey will be used as the basis for further and more ex- 

 tensive exploration of the Arizona crater and other terrestrial me- 



