SECRETARY'S REPORT 71 



and the examination of the internal structure of meteorites from a 

 metallurgical point of view. The plan is to prepare detailed descrip- 

 tions of the topology and morphology of individual meteorites, especial 

 interest being paid to those that show ablation. While very little 

 can yet be said about the total amount of meteoritic material lost, 

 meteorite size and material are both very critical factors. It has been 

 found that small (up to 3 inches in diameter) meteorites are smoothly 

 sculptured ; large stones exhibit shallow elongated pits or depressions 

 (2 cm. by 1 cm. by 5 mm. deep) ; and large irons, very deep pits 

 (5 cm. in diameter and 3 cm. deep). The number, distribution, and 

 size of the depressions depend upon the relation of a particular surface 

 or portion of surface to the direction of flight. Pronounced irregu- 

 larities of shape increase ablation. Finally, heat from the surface 

 seems to penetrate into the meteorite at most only a few millimeters 

 beyond where ablation leaves off. Dr. E. P. Henderson, of the United 

 States National Museum, is actively engaged in this project, which is 

 being supported by the United States Air Force Office of Scientific 

 Research. One of the most difficult and challenging problems facing 

 the present-day aerodynamical engineer is the rational design of pre- 

 flight devices that will withstand the rigors of the passage through 

 the atmosphere. The investigations of the Astrophysical Observatory 

 will yield basic data which may aid in a solution of these problems. 



Dr. F. Behn Riggs, Jr., and Prof. Andrew Lang have nearly com- 

 pleted the design and construction of an electron fluorescent micro- 

 analyzer. The fundamental principle of the instrument is the direct 

 excitation of X-radiation characteristic of the elements of the sample 

 by a fine beam (approximately 5 microns in diameter) of electrons 

 focused on the selected site. The method will be applied first to the 

 determination of nickel-iron-cobalt percentages in meteorites that have 

 Widmanstaetten figures. The method is applicable to microscopic 

 areas or particles. 



An expedition consisting of Dr. John S. Rinehart, Nicholas Matalas, 

 R. O'Neil, and R. Olsen was in residence at the Barringer Meteorite 

 Crater in Arizona during the summer of 1956, to determine the dis- 

 tribution of minuscule bits and pieces of meteoritic material in the soil 

 around the crater. The expedition collected and processed some 700 

 soil samples from over an 80-square-mile area. Especially designed 

 magnetic separators were used to recover the meteoritic material. The 

 results have indicated that the debris lies in a definite pattern; it is 

 symmetrically distributed about a line that runs roughly about 15° 

 north of east; while symmetrical, the distribution is not smooth but 

 contains several local areas in which the abundance of meteoritic ma- 

 terial is high; the crater does not lie at the center of the pattern; and 

 there is a concentration of material to the east of the crater. These 



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