92 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



the nickel-iron ia seen to be made up of grains, part of which show a similarly oriented strong sheen. These are of a 

 very various, highly irregular, angular shape, branching into one another and varying in their dimensions, the majority 

 being 0.02 to 0.03 mm. in diameter, but many sink to 0.01 mm., while others reach the length of 0.5 to 1.5 mm. The 

 larger the grains the more irregularly jagged their shape, as in Hammond ; others, at least in part, are surrounded by a 

 dark border which separates them pretty sharply from one another, and this is here so fine that it only becomes visible 

 on strong magnification and a certain amount of etching. To the naked eye an etched surface appears bright and 

 shining from little reflecting flakes probably belonging to schreibersite. Their minute size prevents determination. 

 Analysis by Fahrenhorst: 



Fe Ni Co Cu Cr S P 



92.00 7.70 0.54 0.03 0.01 0.06 0.24 =100.58 



Specific gravity=7.7568. 



Second, Cacaria obtained by Ward. This piece was cut by Ward himself from the mass in the Mexican National 

 Museum. The principal mass of the nickel-iron appears on weak etching exactly like that of the Vienna piece and 

 shows the same fieldlike portions. The bordering in the latter is, however, different, in that the rows of black grains 

 are lacking, and instead appear little sharply bounded lustrous bands about 0.2 mm. in breadth, probably identical in 

 substance with the isolated rounded to oval taenitelike portions which accompany the black grains. The inclosing of 

 the fields is usually complete, but occasionally the border is interrupted by faces on one side. Further appear between 

 the fields single bands which project on the section in the form of isolated rods. On strong etching here also the chief 

 mass is nickel-iron which appears in irregularly shaped grains the size of which varies in general between 0.5 and 1.5 

 mm. and a part of which show the same strongly oriented sheen. The grains as a rule cut across the above mentioned 

 bands, though occasionally a grain is penetrated by one or more bands. In spite of varying dimensions the distribution 

 of the grains is more uniform than in the Vienna piece. Open clefts of irregular shape extend inward from the natural 

 surface. Hollows occur which are surrounded by a section of the taenitelike substance 1.25 mm. in breadth. In' 

 these fine black, wormlike forms are included grouped into delicate netlike veins, and the same substance seems 

 earlier to have filled the clefts and hollows. Its loss may be due to the manipulation in cutting and polishing. The 

 black inclusions in the "two pieces may be of this nature, although they are distributed in a somewhat different way. | 

 At one point the taenitelike substance fills a cleft. " 



Analysis by Fahrenhorst: 



Specific gravity=7.7070. 



The structural distinction between the two pieces is only quantitative. In the Vienna piece the black particles 

 predominate, in Ward's piece the taenitelike bands. Thus the whole appearance, especially at first sight, is different. 

 It is probable that the higher content in nickel + cobalt in the latter piece is due to the greater quantity of taenitelike 

 substance. 



Finally it may be noted that both pieces have few visible accessory constituents and are pretty easily attacked 

 by acids. This latter observation is not in accord with Brezina's statement that the nickel-iron is almost unattacked 

 by acids. Such a difference in the chemical composition in the parts of one mass has not hitherto been observed in an 

 iron meteorite. 



The meteorite is chiefly preserved in the National Museum of Mexico. 



BIBLIOGRAPHY. 



1. 1867: Tarayre. Surl'explorationmineralogiquedes regions Mexicaines. Archives de la commission scientifique 



du Mexique, vol. 3, p. 270; Paris, 1867. 



2. 1876: Barcena. On certain Mexican meteorites. Proc. Acad. Nat. Sci., Philadelphia; 1876, p. 123. 



3. 1884: Hapke. Beitrage zur Kenntniss der Meteoriten. Abhandl. Naturwiss Verein Bremen, Bd. 8, pp. 513-515; 



also Bd. 9, pp. 358-359. 



4. 1884: von Rath. Verhandl. Naturhist. Verein Bonn, Bd. 41, p. 126 



5. 1889: Castillo. Catalogue, p. 5. 



6. 1890: Fletcher. Mexican meteorites. Mineral. Mag., vol. 9, pp. 152-154 and 156. 



7. 1893: Meunier. Revision des fers meteoriques, pp. 52 and 53. 



8. 1895: Brezina. Wiener Sammlung, pp. 289-290. 



9. 1897: Wulfing. Die Meteoriten in Sammlungen, p. 291. 



10. 1900: Cohen. Meteoreisenstudien XI. Ann. K. K. Naturhist. Hofmus. Wien, Bd. 15, pp. 359-365. 



11. 1905: Cohen. Meteoritenkunde, Heft 3, pp. 400-406. 



