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 



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- 



