322 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



A and B. A weighed approximately 300 grams and B approximately 

 500 grams. The material is sufficiently magnetic that fragments of 

 pea size may be lifted by a bar magnet, and it consists mainly of 

 iron oxides, hydrated in part, with some silicate minerals too highly 

 impregnated with iron oxides to be identifiable, and a little chalced- 

 ony. After fine grinding, specimen A yielded a very small amount 

 (0.06 percent) of metallic iron which was retained on a 90-mesh 

 screen. 



;-'.o- 



L*r.«S< 



I ) 



/ 1 



H^-U. 



,t\y 



J L 



Figure 3. — Diagrammatic sections of a typical meteorite crater. A, fracturing 

 and tilting of strata by outward explosion; B, ring anticline by percussion. 

 (After L. J. Spencer.) 



GENERAL DISCUSSION 



An interesting, paper by Nininger (1948) covers the geological sig- 

 nificance of meteorites. It took scientists many years to accept the 

 fact that matter from outside the earth and its atmosphere was falling 

 and had fallen on the earth's surface. Today there are still some who 

 will not accept the meteoritic origin of some craters. 



It is apparent that studies of craters such as the Meteor crater, 

 Arizona (Barringer, 1909, 1915, 1925), Boxhole crater, Central Aus- 

 tralia (Madigan, 1937), Texas crater (Sellards, 1927; Barringer, 

 1929), Henbury craters (Alderman, 1932), Wabar craters (Philby, 

 1933), Campo del Cielo craters (Nagera, 1926), Siberian craters 



