METEORITES OF NORTH AMERICA. 489 



As the above analysis of cohenite gave a formula (Fe, Ni, Co) 4 C, instead of the formula 

 (Fe, Ni, Co) 3 C obtained for the cohenite of other meteorites, the cohenite of Wichita was 

 studied again by Cohen, 9 and the following result obtained from an analysis by Sjostrom: 



Fe Ni Co C 



90.80 2.37 0.16 6.67 =100.00 



This result gives the formula (Fe, Ni, Co) 3 C. 



The following series of analyses by Manteuffel is given by Cohen: 9 



Fe Ni Co Cu P C 



I. 92.37 6.74 0.59 0.03 0.03 .... =99.76 



II. 92.67 6.71 0.59 0.03 =100.00 



III. 89.36 8.62 0.72 0.02 0.97 0.31 =100.00 



IV. 92.26 7.13 0.58 0.03 =100.00 



I. Analysis of a portion obtained from a section of Wichita. 



II. After deduction of the schreibersite reckoned from the phosphorus. 



III. The chemical composition reckoned from the now accessible determinations, when we assume for the unan- 

 alyzed schreibersite the formula Fe 2 Xi P with 1.30 per cent Co, and identify the angular fragments with the kamacite. 



IV. After deducting schreibersite and cohenite. 

 Jlineralogical composition: 



Kamacite 84. 98 



Tsenite 2. 64 



Schreibersite 6. 34 



Cohenite 6. 04 



100. 00 

 The structure of the iron is thus described by Meunier : 10 



This is a remarkable stone, in which the pencils of schreibersite are quite numerous and exceptionally well 

 oriented. In reality, they are more or less discontinuous and their thickness is not entirely uniform. The angles 

 at which they intersect are entirely conformed to those of the octahedron. The schreibersite consists of masses with 

 more or less irregular outlines often measuring 1 cm. in longest diameter, and a sort of envelope to which other sub- 

 stances contribute, particularly graphite about the pencils of pyrrhotine. These pencils often attain large dimen- 

 sions. One of them measures, in section, 20 by 11 mm. The sulphide contained in them is very pure and of a per- 

 fectly uniform bronze shade; certain cavities appear in them which may have resulted from the process of polishing. 

 The exterior surface is covered with a secondary coating of graphite, very even, compact, and black, unequally thick 

 near the points and whose outlines appear to be nevertheless ordered according to those of the sulphide. There is a 

 minimum of very nearly zero at the two extremities of the small diameter of the kidneys and a very obvious maxi- 

 mum at the two extremities of the large diameter. In many places this envelope of graphite is covered again with a 

 coating of pyrrhotine identical in appearance with that of the central mass, and is separated from the schreibersite 

 envelope by a very thin film of graphite. 



This, as will be observed, is a most remarkable structure, and one which recurs in its most general features in the 

 heart of many other meteoric irons. 



By etching, the Wichita meteorite gives Widmannstatten figures in which the kamacite frequently attains a size 

 of 2 mm. Among these, filaments of tsenite frequently appear, often of an isabell-yellow color which distinguishes 

 them very definitely from the steel-gray groundmass. 



In the above description Meunier seems to have confused schreibersite with cohenite, the 

 latter being an abundant and important constituent of this iron. 



In the Vienna Catalogue for 1895, Brezina 11 further described the structure of Wichita 

 as follows: 



Wichita shows frequent alternations between portions nearly free from cohenite and similar portions bearing 

 cohenite, and is distinguished by the manifold character of the outcroppings of troilite and graphite, which usually 

 show a corona of schreibersite and over this, less frequently, still another zone of cohenite, and finally a coating of 

 swathing kamacite. Graphite and troilite alternate in the lumps which attain as much as 6 cm. diameter, now zone- 

 wise, usually beginning with the troilite in the center, less frequently with the graphite; again, but not so frequently, 

 lying side by side. The graphite occurs as bands between the core and the periphery of the troilite lumps, and thus 

 it has sometimes a perfectly uniform width (in one case of 0.5 mm.) and follows all the inequalities of the exterior. 

 On one place in the trias there occurs an outcropping of cohenite with schreibersite envelope, and more frequently 

 with a corona of cohenite. The schreibersite is for the most part finely porous; the cohenite shows individual fissures, 

 but is otherwise smooth and of a bright luster. 



The name of Brazos has been often applied to this meteorite but if Mallet is right in stating 

 that it was found in Wichita County, Brazos is inappropriate as the Brazos River runs far south 

 of Wichita County. 



The meteorite is chiefly preserved in the University of Texas. 



