File:Bulletin of the Geological Society of America (1903) (20261497118).jpg

Title: Bulletin of the Geological Society of America
Identifier: bulletinofgeolo141903geol (find matches)
Year: 1890 (1890s)
Authors: Geological Society of America
Subjects: Geology
Publisher: (New York : The Society)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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100 W. H. HOBBS—METEORITE FROM A LOOM A, WISCONSIN site at once revealing their position by their fusion, due to the moderate frictional heat of grinding. The larger shallow pittings at h and i, which more resemble the conven- tional "thumb marks,have doubtless been produced in a similar man- ner by fusion of schreibersite, combined with fusion and abrasion of the outer walls, since their sides toward the meteorite center possess the same steep, irregular slopes as the others, with some accumulation of oxide scale. Being located near the circumference of the disc, they lie within the zone of maximum erosion from the action of the compressed
Text Appearing After Image:
Figure \.—-Diagrammatic Sketch of Meteorite's convex Surface. Designed to serve as a guide to plate 3. The area outlined by the dotted line is the nearly flat central boss. The spirally radial lines of the margin are ridges and grooves, and their Isevo- rotatory character is somewhat exaggerated in the sketch, a a, dents due to pounding with a rock at the time meteorite was discovered ; b b, grooves produced by attack with cold chisel; c, a portion of the margin abraded by a file; d, file scratches ; e,f, g, deep pits produced by fusion and removal of schreibersite; 7i and i, "thumb mark" pittings due to fusion of schreibersite in the marginal zone of erosion (larger in plate 5); /, saw-cut stopped by encountering schreiber- site ; A; I and m n, saw-cuts. air, and the thin walls which presumably once separated them from the present circumference of the meteorite would be hardly able to withstand the erosive action. The marginal area of the meteorite front, on which the pittings h and i are found (for convenience called the straighter margin) is in rather sharp contrast with the opposite front margin (the lobate margin). From the nearly plane central boss of elliptical shape (axes, 9 and 7 centimeters) the surface of the disc slopes away sharply on the side of the larger pit-

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