COLLECTIONS OF METEORITES IN AMERICAN MUSEUM 31 



panwion and coiitraetiou of the mass just as 

 joint planes are developed in rocks of the 

 earth's crust, or, that they were developed 

 at the time of the fall by impact. 



The iron meteorites have a thinner crust 

 or skin than the stone meteorites. The iron 

 skin has a metallic luster and is not so black 

 as the crust of the aerolite. The interior of 

 these specimens, like the aerolites, was not 

 affected by their passage through the zone 

 of fire, the atmosphere, for their texture is 

 unaltered up to the very skin. In some iron 

 meteorites peculiar crosslines known as 

 "Widmanstatten" or "Neumann lines" may 

 be etched on a polished surface by a weak 

 solution of nitric acid. For some time it 

 was supposed that this was a sure way of 

 identifying meteorites, but there are a num- 

 ber of siderite meteorites in the collection 

 which cannot be etched. Their outer sur- 

 faces may be chiseled into a nose, rounded, 

 or pitted, depending upon whether they 

 turned over in their rapid flight. The most 

 striking instance in the Museum of a pro- 

 tuberance shaped in this manner by the 

 compresse<l oxygen flame on a siderite, is 

 the large Willamette, Oregon, specimen. 

 The back side of the specimen is rough and 

 deeply scarred, while the front has a 

 rounded, pitted, and fluted surface. 



There is also in another one of the alcove 



cases on the east side of the hall of geology 

 and invertebrate paleontology one of the 

 tliree collections of material which have been 

 gathered from Meteor Crater. This exhibit 

 has been placed here through the courtesy of 

 I'rineeton University, and of Mr. D. M. Bar- 

 ringer, of Philadelphia. Another exhibit is 

 at the United States National Museum, 

 Washington, and a third one at the Crater 

 itself, in Coconino County, Arizona. 



Some years ago a company was organized 

 under the direction of Mr. Barringer, which 

 surveyed the site and sank drill holes in the 

 bottom of the Crater to depths greater than 

 five hundred feet. The products of the drill- 

 ing, samples of the sedimentary rock, meta- 

 morphosed sandstone, shale balls, Canyon 

 Diablo meteorites, and ejected rock frag- 

 ments are on exhibition. A booklet written 

 by Mr. Barringer containing a number of 

 maps, photographs, and descriptive text 

 accompanies the exhibit. 



On an average of once a week the Museum 

 is called upon to examine supposed meteor- 

 itic material, but in most instances we are 

 obliged to tell the expectant visitor that his 

 specimen is some other kind of rock. It 

 should be noted that if the thin metallic skin 

 or black crust is absent, the specimen is in 

 all probability not a meteorite. 



Chester A. Reeds. 



Rear view of the Willamette meteorite to show the effects of the flames, whipped backward in the 

 speed of the flight and the fierceness of the burning. This meteorite, now in Memorial Hall of the Amer- 

 ican Museum, was found in Willamette Valley, near Oregon City, Oregon, November 9, 1906. [See the 

 back of the cover for another view of this meteorite] 



