METEORITES OF NORTH AMERICA. 205 



depressions larger ones are present which reach the length of a millimeter and are arranged in zones 0.5 to 1 cm. distant 

 from each other, within which they are quite regularly arranged in their longest direction. These are surrounded by a 

 common dull zone in which only the finest etching lines can be recognized. The other needles are apparently arranged 

 regularly, but it can not be determined whether they lie parallel to the three directions of the cube or not. On account 

 of the great number of fine rhabdites and the depressions referable to these it is difficult to determine how much the 

 etching pits have to do with the lively, oriented sheen. Fort Duncan seems to be poor in larger accessory constituents. 

 Both Sanchez Estate and Fort Duncan acquire strong permanent magnetism and possess quite strong cohesive force. 

 After strong heating and slow cooling a piece of Fort Duncan acts like soft iron, while rapid cooling after heating to a 

 bright red is without effect. Leick's 17 determination of the specific magnetism of Fort Duncan on a triangular piece 

 is .27 and on Sanchez Estate .69 units per gram. Among the constituents isolated by dilute hydrochloric acid from 

 Sanchez Estate were single rhabdites 0.25 to 0.66 mm. thick and 1.33 mm. long which were suitable for crystallographic 

 study. There were also granules of chromite and silicates. The majority of the rhabdites consist of very fine needles 

 which are semewhat larger in cross section than those of Coahuila. They are generally from 0.05 to 0.02 mm. in width. 

 Thin plates of schreibersite occur in small numbers also. Daubreelite could not be found in a piece weighing 35 grams. 

 Analysis of the rhabdite of Sanchez Estate gave: 18 



Fe Ni Co P Residue 



55.01 28.63 0.60 15.24 0.71 =100.19 



The composition of Sanchez Estate calculated from the isolated constituents is as follows: 

 Fe Ni Co Cu P Residue 



92.25 6.96 0.53 0.01 0.23 0.02 =100 



Since no complete analysis has been made of Sanchez Estate it is not certain whether it possesses a so much higher 

 content of nickel and cobalt than Fort Duncan or Saltillo, as the above analyses would indicate, or whether the analysis 

 is incorrect. 



The mineralogieal composition of the three irons calculated from analyses is as follows: 



Nickel-iron. Rhabdite. Troilite. Daubreelite. Chromite. 



Sanchez Estate 98.49 1.49 0.02 =100 



Fort Duncan 97.66 1.48 0.73 0.11 0.02 =100 



Saltillo 98.83 1.17 .... .... .... =100 



According to the above observations Fort Duncan is distinguished by a considerably smaller number of short 

 etching lines, the appearance of large rhabdites distributed in layers, scarcity of accessory constituents, resistance to 

 acids, and perhaps by lower content in nickel and cobalt. 



These meteorites do not seem to have been much distributed. According to Clarke's 

 Catalogue, 105 kgs. of Sancha Estate is in the U. S. National Museum, although Tassin's Cata- 

 logue does not list it. Brezina's Catalogue of 1895 lists 12 kgs. of Fort Duncan. 



BIBLIOGRAPHY. 



1. 1854: Genth. On a new meteorite from New Mexico. Amer. Journ. Sci., 2d ser., vol. 17, pp. 239-240. 



2. 1855: Smith. Memoir on meteorites. — A description of five new meteoric irons, with some theoretical considera- 



tions on the origin of meteorites based on their physical and chemical characters. Amer. Journ. Sci., 2d 

 ser., vol. 19, pp. 160-161. 



3. 1863: Rose. Berlin Sammlung, p. 49. 



4. 1870: Burkart. Ueber die Fundorte mexicanischer Meteoriten. Neues Jahrb. Min., pp. 673-682 and 690. 



5. 1881: Shepard. On a new meteoric iron, of unknown locality, in the Smithsonian Institution. Amer. Journ. 



Sci., 3d ser., vol. 22, p. 119. 



6. 1885: Hidden. Preliminary note on an iron meteorite from Maverick County, Texas. Trans. New York Acad. 



Sci., vol. 5, p. 231. 



7. 1886: Hidden. A new meteorite iron from Texas. Amer. Journ. Sci., 3d ser., vol. 32, pp. 304-306. 



8. 1886: Brezina. Neue Meteoriten II. Ann. K. K. Naturhist. Hofmus. Wien, Bd. 2 (Not.), pp. 25-26. 



9. 1887: Huntington. On the Coahuila meteorites. Amer. Journ. Sci., 3d ser., vol. 33, pp. 115-118. 



10. 1887: Meunier. Examen mineralogique du fer meteorique de Fort Duncan (Texas). Comptes Rendus, Tome 



104, pp. 872-873. 



11. 1889: Huntington. The crystalline structure of the Coahuila irons. Proc. Amer. Acad. Arts and Sci., vol. 24, 



pp. 30-35. 



12. 1889: Cohen. Sao Iuliao. Neues Jahrb., 1889, vol. 1, pp. 227-228. 



13. 1890: Fletcher. Mexican meteorites. Mineral. Mag., vol. 9, pp. 99, 103-119, 174-175. 



14. 1892: Linck. Ueber die Zwillingsbildung und den orientirten Schimmer am gediegen Eisen. Zeitschr. fur 



Krystallogr., Bd. 20, p. 215. 



15. 1893: Meunier. Revision des fers met£oriques, pp. 14-15 ,17, 19, and 21-22. 



16. 1894: Cohen. Meteoresien-Studien III. Ann. K. K. Naturhist. Hofmus. Wien, Bd. 9, pp. 102-107. 



17. 1895: Cohen. Meteoreisen-Studien IV. Idem, Bd. 10, pp. 82-86 and 89. 



18. 1895: Brezina. Wiener Sammlung, pp. 290-291. 



19. 1905: Cohen. Meteoritenkunde, Heft 3, pp. 188-195. 



