354 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



Genth's 4 account of it, as copied in the American Journal of Science from the Report of 

 the Geological Survey of Pennsylvania, was as follows : 



A chemical examination of tho Pittsburgh meteorite yielded the following results: Its specific gravity, which 

 Shepard gave as 7.380, was found to be 7.741, the average of three closely corresponding determinations by Dr. Koenig, 

 Dr. Headden, and myself. After polishing and etching with dilute nitric acid it presents Widmanstatten figures, 

 which are produced by inclosed schreibersite. In the section which has been made it happens that most of the 

 exceedingly minute schreibersite crystals are cut across and are seen as small dots on a frosted surface; some appear 

 as minute needles, arranged in parallel lines like the trees in an orchard. A few elongated patches of a whiter nickel- 

 iron alloy are also visible. 



The analysis of a somewhat oxidized piece gave the following composition: 



Fe Ni Co Cu Mn S P 



92. 809 4. 665 0. 395 0. 034 0. 141 0. 037 0. 251 =98. 332 



Brezina, 5 in 1885, classed the meteorite as a hexahedrite with twinning lamellae, also show- 

 ing cubic cleavage and Neumann lines. With it he placed Lime Creek, Coahuila, Braunau, etc. 

 He had, however, only a piece of 2 grams for investigation. 



Cohen 7 investigated the 99-gram specimen of this iron in the Gottingen University col- 

 lection. He described it as follows : 



It was a very irregular piece with ragged edges, and had evidently been cut with a chisel from the mass and from 

 the peripheral portion of the latter, since there seemed to be small flat parts of the border of the original surface of the 

 meteorite. By cutting, a surface of 4 sq. cm. was obtained. 



Etching proved that Millers Run is actually, as Reichenbach stated, an octahedrite. The coarse lamellae are for 

 the most part of an irregular lumpy form, sometimes also elongated and regularly bounded. Some of the bands lie 

 immediately upon one another, others are divided by a minute cleft; between many of them, however, a distinct 

 tsenite band is found, which at the point where several lamellae cluster together broadens out into somewhat large, 

 triangular portions. That no schreibersite is present is easily proven by testing the ductility with a fine needle. As 

 usual in coarse octahedrites, plessite is very inconspicuous; the tiny little portions are rich in combs. 



The kamacite acts differently. At some distance from the original surface of the mass it is coarse-grained, shows 

 distinct hatching marks and numerous uniformly distributed etching pits; the more granular it is the less prominent 

 are the hatchings, while the etching pits remain about the same in amount. In a few bands numerous small, brightly 

 glistening rods are found, which appear to be schreibersite. 



An outer zone of from 1 to nearly 1.5 cm. in breadth, whose border runs in a wavy or serrated outline, but which 

 is abruptly cut off and does not coincide with the boundaries of the lamellae, appears much altered. It is duller and 

 darker than the interior of the meteorite, and the kamacite is spotted, while very irregular particles as much as 0.5 

 mm. in size are distinctly differentiated from one another by a lively oriented luster, though not sharply separated. 

 The coarse granulation of the bands is obscured or entirely disappears. 



This is undoubtedly a zone of alteration; whether it is original or not, or whether the piece under investigation 

 was partially heated in the working up of the main mass and then cut off, must remain uncertain. The latter may 

 be more probable, since in the case of so large a mass (132.5 kg.) a considerably narrower zone of alteration is 

 usually met with, unless, indeed, this should be a tonguelike projection. 



The only accessory material observed was a few small particles of schreibersite. 

 The analysis by Hildebrand gives the following figures: 



Fe Ni Co Cu Mn Cr S P Chromite 



93.38 5.89 1.24 0.05 0.00 0.02 0.07 0.15 0.07 =100.87 



This gives the following mineralogical composition: 



Nickel iron 98. 78 



Schreibersite 0. 96 



Troilite 0. 14 



Daubreelite 0. 05 



Chromite 0. 07 



100. 00 



As stated by Silliman, 1 only a little of the mass has been preserved. Wulnng lists 592 

 grams, of which the Yale collection possesses 213 grams, and the British Museum 208 grams. 



BIBLIOGRAPHY. 



1. 1850: Silliman. Notice of two meteoric irons. Proc. Amer. Assoc. Adv. Sci. Fourth meeting held at New Haven 



(1850), p. 37. 



2. 1851: Shepard. On Meteorites. — 6. Specific gravities of two meteoric irons: "Meteoric iron of Pittsburg, Pa., 



7.380." Amer. Journ. Sci., 2d ser., vol. 11, p. 40. 



