628 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 



Outside of the earth's atmosphere, meteorites move at high speeds, 

 estimated to be around 25 to 50 miles per second. This speed through 

 the air enveloping the earth brings about a pressure on the meteorite 

 of about 10,000 pounds per square inch, and if the meteor is of friable 

 stone it is crushed to fragments. " If the meteorite is of iron it may 

 withstand the pressure, but in either case it catches fire and may l)e 

 completely consumed. ... It has been calculated that any iron 

 meteorite must lose 90 pev cent of its substance by being burned 

 away in its passage " to earth. Not over three or four are found 

 each year, and the number of all the iron and stony meteorites in the 

 museums of the world is less than 1,000 and their total weight not 

 over 200 tons. (1925.) 



Meteorites on entering our atmosphere are greatly retarded and 

 usually fall on the earth with speeds up to several miles per second. 

 Some have been seen to fall so slowly as to rebound on striking ice, 

 without either being broken, and others have buried themselves in the 

 soil to depths of 5 feet and one went down to 11 feet. The stony 

 meteorites range in size up to 660 pounds and the iron ones to 36.5 tons 

 (Cape York, west Greenland). Of all the known meteorites about 

 one-half have been seen to fall and have then been found (these are 

 called " falls ") ; others, discovered without having been seen to fall, 

 are labeled " finds." Of the falls only 10 are irons, and accordingly 

 most of the metallic ones are finds. Usually a fall consists of a 

 single specimen, but among the stones the individuals of a single fall 

 number at times thousands and in two cases each fall yielded as many 

 as 100,000 stones. 



Constitution of meteorites. — The meteorites of celestial space show 

 " so great a uniformity of material yet so individualized that one 

 conversant therewith can tell almost at a glance whether celestial 

 or terrestrial in origin." (1930: 47.) 



" The elemental matter of meteorites is the same as that of the 

 earth." In meteorites there are surely known 10 common and 18 

 rarer elements ; 7 other elements have been reported but as yet these 

 are not proved. " Though the elemental matter of meteorites may 

 be the same as in terrestrial rocks, the form of combination is at times 

 radically different and of a nature to indicate that they formed 

 under conditions quite unlike those existing on the earth to-day, and 

 particularly so with reference to the presence of free oxygen and 

 moisture." (1916a: 1, 5.) One of the minerals known in meteorites 

 is mernUite, first noted and described by Merrill, and named by 

 Wherry in 1917 in honor of its discoverer. Farrington (1930) de- 

 fines it as " a calcium sodium phosphate, differing in composition 

 from any known terrestrial mineral." 



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