392 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



Specific gravity, 7.015 to 7.112. It appears to contain no chlorine. It gave — 



Fe 92. 096 



Ni 2. 604 



Schreibersite 5. 000 



Cr, Co, Mg, and P traces 



Residue of Fe 2 3 , Si 2 , and C. 



99. 700 



Brezina, 3 in 1885, grouped the meteorite in the Arva group, and remarked that it resem- 

 bled Wichita, since it showed hatching. 



Meunier 4 classed the meteorite as arvaite. He remarked concerning it as follows : 



The museum possesses only a small specimen of the meteoric iron found in 1863 in the southeastern part of the 

 State of Missouri, but the specimen suffices to show the identity of its substance with that which forms arvaite. 



The schreibersite is much less abundant than in the Sarepta iron, but it has in the main the same disposition and 

 the same characteristic kamacite bands of the arvaite type. Pyrrhotine is visible here and there, and in its neighbor- 

 hood are found graphitic lamellae which complete the resemblance to the type. 



Cohen 5 remarked that cohenite was probably present in the meteorite. He gives the name 

 St. Francois County as a synonym of southeast Missouri. 



Brezina, 6 in 1895, also used the name St. Francois County with southeast Missouri as a syn- 

 onym, but does not give the origin of the name St. Francois County. He states that a plate 

 was acquired which gives a complete section through the iron. He says: 



It shows a regular structure. The lamellae are long, straight, grouped, but slightly puffy. Taenite is very scarce, 

 field subordinate, very like the bands; ribs of cohenite quite numerous in the kamacite in the form of individual 

 grains; kamacite very uniformly grouped. 



Wiilfing 7 grouped St. Francois County and southeast Missouri together, quoting Cohen 

 and Brezina. He notes a total weight of 2,418 grams. 

 Cohen 8 made a study of the meteorite as follows : 



Although Shumard gives the weight of the original southeastern Missouri at 340 grams, Bement, Ward, and 

 Vienna possess 2 kgs. of St. Francois County, so that a second larger piece must have been found later, which under 

 the name of St. Francois County, as it seems given by Kunz, was brought into commerce without a notice of it hav- 

 ing been made in literature. A brief note from Brezina informs me that the pieces of St. Francois County, in Vienna, 

 were obtained through Kunz from the Bement collection and correspond completely with the older southeastern 

 Missouri. Two pieces were placed in my hands for investigation of the structure; one from the Vienna Museum weigh- 

 ing 288 grams and the second from the Griefswald collection weighing 30 grams. The following points may be noticed 

 in addition to the characteristics stated by Brezina: Besides some few fields made up of little kamacite rods and 

 intercalated taenite foliae occur portions of a field-like appearance which, however, consist of short puffy lamellae with 

 etched lines running in a single direction. They are evidently what Brezina designated as bands resembling fields. 

 It may be questioned whether such portions should be referred to fields. They may be kamacite individuals in which 

 occur short combs which are intergrowths of the bordering taenite, which is not the case in the normal bands. As was 

 shown by Brezina, and as is usual in coarse octahedrites, the fields of St. Francois County are subordinate. The tro- 

 ilite mentioned by Ward and Meunier is lacking in my sections, also the graphite-like lamellae mentioned by Meunier. 

 The distribution of these accessory constituents is evidently thus very unequal. On the other hand, the ribs of cohen- 

 ite mentioned by Brezina occur in the bands in the form of grains and small prisms 7 mm. long and .6 mm. broad; 

 also large schreibersites which do not, like the former, lie with their principal direction parallel to the bands. In the 

 immediate neighborhood of the largest schreibersite occurs a zone 4 to 6 mm. broad of granular kamacite, the size of 

 the grains rising to 1.5 mm. Since granular kamacite does not occur elsewhere, the schreibersite has probably influ- 

 enced the crystallization of the nickel iron. The cohenite ribs are smaller and more sparingly present than are the 

 crystals composed directly of cohenite in Magura, Beaconsfield, Bendego, and related irons. Most of the bands lack 

 them entirely. Rhabdite occurs in crystals from 0.003 to 0.04 mm. thick. It can not be directly observed, but 

 remains behind on dissolving pieces in dilute acid. Where the plates have a natural surface, black, hard portions 

 extend into the nickel iron which resemble the so-called iron glass. A piece weighing 14.082 grams was analyzed by 

 Fahrenhorst, with the following result: 



H 2 12. 28 



Fe 2 3 93. 52 



NiO+CoO 7. 76 



113. 56 

 This shows a mixture of iron hydroxide with nickel iron, and indicates a rust crust which has penetrated by 

 clefts into the nickel iron. 



