AMERICAN METEORITES—HENDERSON 
become interested in learning what 
made this “‘rock” too heavy. 
The origin of meteorites is a con- 
troversial subject and has been pur- 
posely omitted from this discussion, 
but their composition brings to mind 
the material believed by geologists to 
occur in the interior of large planets 
like our earth. In what manner the 
planet or planets were broken up and 
how long these individual objects have 
existed as fragments in outer space 
before falling upon our earth is a 
problem for the astronomer. Me- 
teorites, before falling to the earth, 
existed in an environment very differ- 
ent from that here. They were never 
exposed to much oxygen or water; 
hence, in their new terrestrial environ- 
ment they become subjected to new 
chemical conditions, and alteration 
starts rather quickly. The metallic 
iron in some meteorites soon combines 
with oxygen and water, and a rust 
develops on the metal which is similar 
in appearance to ordinary iron rust. 
No simple method has been devel- 
oped to determine how long a weath- 
ered or rusted meteorite may have 
been on this earth when it is found. 
Weathering conditions and the nature 
of the soil in which the meteorite fell 
differ from place to place, and also 
some meteorites are less stable or less 
resistant to weathering than others. 
Meteorite Craters 
The most spectacular feature con- 
nected with any meteorite in the world 
is the large meteorite crater in Arizona. 
This is the site where the largest known 
meteorite crashed into the earth in 
prehistoric times. The crater is nearly 
circular in shape, with a diameter of 
about 1,200 meters and a depth from 
the rim to the crater floor of 175 
meters. This great depression, made 
by the impact of a falling meteorite, 
still represents the greatest explosion 
ever to have taken place on the earth 
other than some of volcanic origin. 
Around the rim of the crater many 
large masses of meteoric iron have 
been found. Over 5,000 kg. of me- 
261 
teoric material has been reported, and 
in addition countless small fragments 
have been carried away. Canyon 
Diablo is the name given the meteoric 
iron from this crater, and it is perhaps 
the best-known meteorite in the world. 
The literature on it and on the crater 
is so extensive that it is not feasible to 
cite it. 
Within the lifetime of many now 
living, our earth was struck another 
terrific blow by a falling meteorite. 
In 1908 a large one fell in Siberia and 
leveled the forest for miles around. 
Although no fragments of this have 
been found to date, there is no ques- 
tion but that this explosion was caused 
by a meteorite. 
There are some other well-known 
craters in our country from which 
meteoric material has been obtained. 
The second largest is the Odessa, Tex., 
crater, which has a diameter of about 
170 meters but a depth of only 5 
meters. ‘The third largest is the 
Brenham, Kans., crater which is about 
17 meters in diameter and about 3 
meters deep. 
The National Collection of Meteorites 
The collection of meteorites in the 
United States National Museum con- 
tains representative samples of 379 o1 
the 524 different meteoritic falls which 
have occurred in this country. This 
is slightly more than 70 percent of all 
known American meteorites, and con- 
stitutes an adequate representation of 
the different varieties and peculiarities 
of meteorites. 
Meteorites may fall anywhere on 
earth, and it is now known through 
specimens which have been identified 
and preserved in collections that there 
have been about 1,450 different falls 
and finds of meteorites. There are 
specimens of 388 different falls from 
outside the limits of our country in the 
National collection; these are sizable 
samples that adequately represent the 
meteorites. The collection thus con- 
tains representative samples of 52 per- 
cent of the known meteoritic falls in 
the world and hence is an important 
