COLLECTIOXS OF METEORITES L\ AMERICAN MUSEUM 29 



are unevenly mixed, that the oxygen is neg- 

 ligible or absent in places, and that there 

 are "holes" in the upper atmosphere such 

 as the aviators have experienced in the lower 

 atmosphere ? Perhaps there are a series of 

 "crushing" stages throughout the flight of 

 the meteor, which develop a larger number 

 of smaller fragments and greatly increased 

 rate of wastage by combustion (see Dr. 

 Thomson's article, page 27). This would 

 explain the enlargements in the meteor trail, 

 but it does not meet the objection raised by 

 the total disappearance of the light streak 

 and its renewal subsequently as seen in one 

 of the photographs. 



The Museum collection contains a large 

 number of stone meteorites (aerolites), as 

 well as of iron meteorites (siderites), and 

 a representative lot of the intermediate 

 group of siderolites, which, speaking broadly, 

 are part stone and part iron. The large 

 stone and iron meteorites in the Museum col- 

 lection are in Memorial Hall at the entrance 

 to the Museum. The smaller stone, iron, and 



siderolite specimens are in alcove cases on 

 the east side of the hall of geology and in- 

 vertebrate pala?ontology, fourth floor, central 

 wing. 



The exterior of a stone meteorite is cov- 

 ered with a black crust about one thirty-sec- 

 ond of an inch thick or less. The interior of 

 such a specimen is unaltered, and on re- 

 cently broken surfaces is usually of a light 

 gray color. Where the aerolite has lain on 

 or just beneath the earth's surface for a 

 long time, both the exterior crust and 

 chipped surfaces may be dulled by weather- 

 ing, for even stone meteorites oftentimes 

 contain considerable iron-bearing minerals 

 which oxidize, thus discoloring the surface. 



The Selma aerolite, from Selma, Alabama, 

 in Memorial Hall, is the largest stone me- 

 teorite ever found in this country and one 

 of the largest in the world. Several cracks 

 are in evidence in this meteorite, but 

 owing to the absence of a crust within the 

 cracks, it is supposed that they developed 

 after it reached the earth by alternate ex- 



The stone meteorite has a black crust one thirty second of an inch thick or less, and on freshly 

 broken surfaces is light gray in color. Stone meteors, of course, break and scatter during flight much 

 more readily than iron meteors 



