118 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



Meunier 5 made the following note on an oxidation product of the iron: 



It presents a curious phenomenon with which the chemists do not seem to have concerned themselves. This 

 consists of a very remarkable bright green effloresence, in striking contrast with the yellowish shade of the meteorite 

 itself. This effloresence does not seem to be referable, to any considerable extent, to iron, but appears to be composed 

 especially of chloride of nickel. It was kept in the air for over two years without changing color, which would not 

 have been so in the case of a ferruginous chloride. 



Some later study of the meteorite was made by Meunier 8 as follows: 



It weighs 780 kg., and is about 1 m. in height, 47 cm. in length, and 37 cm. thick. The natural surface appears 

 almost entire, but there is no crust like that of the iron of Braunau. This crust has, without doubt, been destroyed 

 by oxidation. The general form of the mass is that of a truncated triangular pyramid, the edges of which are blunted. 

 Upon its surface may be seen depressions such as have been mentioned. Some of these are very large, forming veri- 

 table basins, and upon their walls are a great number of small pits of various size. At one point also may be seen little 

 depreesions joining one another and resembling, in spite of the evident difference of origin, impressions made by drops 

 of rain falling upon a soft substance. Some of the cylindrical cavities seem to be due to the disappearance of troilite, 

 like those upon the iron of Charcas. A polished slab gives Widmanstatten figures of much neatness. 



On page 21 of the same work Meunier gives an analysis of the graphite of Charcas. He 

 found Carbon 98, Iron 0.9 = 98.9. Specific gravity, 1.309. On page 23 he states that the 

 nickel-iron is naturally passive. On page 39 he gives a colored plate showing Widmanstatten 

 figures brought out upon the iron by heating. These, he states, are of the character of long, 

 fine, yellowish lines upon a ground of bluish color. 



The specific gravity of the iron, p. 118, is given as 7.71 and its composition "after an 

 approximate analysis made in the geological labratory of the museum" as follows: 



Fe Ni Si Sulphide Insoluble residue 



93. 01 4. 32 trace trace 0. 70 =98. 03 



The insoluble residue, Meunier states, contains 25.584 per 100 of schreibersite and a large 

 proportion of graphite. 



Brezina 7 remarks regarding Charcas as follows : 



Charcas, as well as La Caille, shows 'numerous tiny grains of troilite along the tsenite and sometimes in the kamacite 

 also. Laminae 0.75 mm. wide. 



Fletcher- 8 gives a brief history of Charcas and thinks, on account of the similarity of figures 

 with Catorce and the fact that a good wagon road runs from Charcas to Catorce, that they were 

 a part of the same fall. This conclusion is not generally accepted, however. 



Meunier, 9 in his revision, describes the structure further as follows: 



This iron would serve as well as that of La Caille for the representative of its type. It differs distinctly, however, 

 from the French iron and should not be confounded with it. The kamacite bands are of medium width. Plessite is 

 much less abundant than in the Caille iron, the hatching is less conspicuous, and it shows small patches of pyrrhotine 

 very much carburetted. These latter appear also in very peculiar line series in the interstices of the kamacite bands. 



Brezina 10 in 1895 further remarks regarding Charcas as follows: 



Charcas is distinguished from all other Mexican irons by reason of the very uniform distribution of troilite in dots 

 all through the iron. According to Castillo it weighed 578 kgs. when it reached Paris. Fletcher identified it with 

 Catorze and Descubridora, but I do not hold this proven on account of the constant occurrence of troilite and because 

 of certain differences of structure. A recently acquired piece shows the already noted slight crumpling of the laminse, 

 kamacite slightly hatched, dotted with fine specks; the tsenite strongly developed, fields very distinctly marked out 

 and filled with finely flecked trias. Upon one cut surface occurs a troilite-bearing concretion of schreibersite about 

 1 cm. in size. Many cracks run parallel with the octahedral laminse from the*exterior toward the interior. 



Cohen 10 found that the iron took on more or less strong permanent magnetism, although, as 

 his result differed from that of Meunier and the piece was small, he thought that possibly he did 

 not have a genuine piece of Charcas. 



The meteorite is chiefly preserved in the Natural History Museum at Paris. The Ward- 

 Coonley collection possesses 3,200 grams. 



filBLIOGRAPHY. 



1. 1804: SONNESCHMID. Mineralog. Beschreibung der vorziiglichsten Bergwerks-Reviere in Mexico oder Neuspanien' 

 p. 288. (In manuscript, copies in the K. K. Naturhist Hofmus and at Freiberg.) 



