162 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



Of the masses mentioned in the foregoing, the most important is the one weighing 576 kg., 

 which was fully described by Burkart 12 as follows : 



In the year 1830 I learned of the existence of a large mass of meteoric iron within the bounds of the Hacienda 

 of Poblazon, and soon afterwards I saw a smaller meteoric iron mass in the possession of a friend, said to have come from 

 the neighborhood of Alamos de Catorze. Later, in 1856, 1 learned that the mass from Poblazon, estimated at 18 cm. 

 weight, had been brought by a Mr. Aguilar to his amalgam works situated at Catorze, in order to make of it a base for 

 a stamp mill for this work; and in the course of the year 1S73, Prof. Don Antonio del Castillo, of Mexico, informed 

 me that this meteorite had been brought from San Luis Potosi to the capital city of Mexico without, however, stating 

 how, when, or from whence the same had come to San Luis Potosi. Further particulars concerning this iron meteorite, 

 only the locality of which has been known hitherto, are found in the journals of two Mexican scientific societies for 

 geography and statistics and for natural history, from which, therefore, we have drawn the following: 



The Society for Geography and Statistics obtained already in the year 1871 an iron meteorite sent from San Luis 

 Potosi, and later also, according to their desire, an historical notice of the same. They appointed a commission to 

 investigate and describe the meteorite, which, with reference to its approximate place of discovery, they designated 

 as the aerolite of Descubridora, and to install the same in the building used by the society as the nucleus, with other 

 objects already in hand, of a collection of natural products and works of art. This determination, however, was later 

 changed and a distribution of the mass, under the direction of the commission, was determined upon in order to be 

 able to make an exhaustive investigation of it. This determination called forth sharp censure from different quarters 

 because the great meteoric iron mass was at the time regarded as Mexico's finest meteorite, and its destruction was 

 given up in order to preserve it inviolate for posterity. * * * 



The meteorite of Poblazon was found certainly between the years 1780 and 1783 upon the mountain of Descu- 

 bridora, in the neighborhood of the mining region of Alamos de Catorze, a district noted for its rich diggings of silver 

 ore, and therefore even yet designated as Descubridora. It reached San Luis Potosi in the year 1871, in charge of 

 Vicento Irizar, for the Society of Geography and Statistics in Mexico. 



Its form was described as that of a distinctly marked prism, with an egg-shaped base of 90 cm. Its weight was 

 given as 575 kg., and it was noted that its mass was of a whitish, steel-gray color, very tough, of a fibrous texture, and, 

 on account of its great density, capable of taking a beautiful polish. 



The mass was cut in two pieces, the larger of which was 60 cm. long. From this, however, there had been cut a 

 slice 4 cm. thick which was said to have been divided up into smaller pieces among the public collections and chem- 

 ical laboratories of the land. 



The section surfaces of both the larger pieces are said to have been engraved, upon one surface the national arms, 

 upon the other information as to the place of find, the date of same, the name of the donor, the original weight, the 

 volume, the results of analysis, and the physical characteristics of the meteorite. The particles resulting from the 

 cutting of the iron are said to have been used for the purpose of manufacturing a knife blade, an elastic spring, a 

 wire, etc., in order to determine the malleability, hardness, and toughness, as well as the practical uses of the 

 meteorite; then, according to the specifications in the instructions of the commission of the Society of Geography and 

 Statistics, the smith of the Hacienda San Miguel, near Poblazon, had already made hatchets and nails of a few frag- 

 ments cut from the meteorite which, on account of their durability, were very much prized. 



The mass must, therefore, at an earlier time have been larger, heavier, and of somewhat different form than it 

 appears to have been at the time of its investigation in Mexico, even though Aguilar, its former owner, is said not to 

 have carried out his intention of making a stamp mill base of the iron. 



In the second of the foregoing, the commission of the Society of Natural History gave a somewhat more complete 

 description of the meteorite of Poblazon, or Descubridora. They found at the beginning of their activity that the 

 meteorite had already been cut in two, and they could not, therefore, as they themselves assert, form an even approxi- 

 mately correct idea of its general form, but concluded from the form of the piece and from the data in the first report 

 that the meteorite had a distinctly pyramidal form. 



In the meantime, however, the commission had also obtained photographs which had been taken from the iron 

 mass in San Luis Potosi, and which, are said to have shown the three flat surfaces of the pyramid. These surfaces show 

 in their outline a few straight lines which for the most part correspond to the direction of the cleavage planes, since by 

 prolonging the most distinct of these lines, according to the opinion of the commission, figures should be obtained which 

 resemble the figures obtained by treating the polished surfaces of the meteorite with nitric acid, and among the angles 

 formed by the intersection of the lines, the angle of 109°, corresponding to the octahedron, may often be recognized. 

 Moreover, the commission noted, upon one of the surfaces, a crack parallel with the line of the contour, and between 

 the two another blackish line which meets with the line proceeding from another point. 



The color of the iron in places exposed to the atmosphere is brownish-black ; in some other places on which schrei- 

 bersite appears to be exposed it is, on the contrary, silver white, and upon a fresh fracture whitish, steel-gray. It shows 

 a distinct crystalline structure, and has in general a little metallic luster, but on the oxidized exterior is dull. 

 Hardness=8; flexible and malleable; specific gravity=7.38. Both poles of the magnetic needle were attracted by 

 the iron. 



On the inside of the meteorite occur some cavities which were filled with a crystalline, earthy (?) mass of speist 

 gelbe color shading into tom-back brown, and with a metallic luster, the troilite of Haidinger or iron sulphide. 



Analysis by Patricio Murphy: 



Fe Ni Co S Cr, P, O loss 



89.51 8.05 1.94 0.45 0.05 =100 



