220 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



In the lighter lamellselike particles the irregular, jagged grains are about 0.02 to 0.04 mm. in size ; in the darker, dull , 

 plessitelike portions they are only one-fourth as large, and in the fine, dark-gray seams they are still finer, so that 

 here the individual grains are not distinctly marked from one another. Where this is the case, it is distinctly 

 apparent that each grain is surrounded with a dull, black, somewhat sunken zone 0.005 mm. wide, which apparently 

 consists of nickel-iron more readily attacked by acid. The same forms a fine, black network, whose now coarser, 

 now finer meshes are filled with light nickel-iron. Since the threads are all of approximately the same breadth, they 

 come out the more prominently the smaller the meshes are, and therefore the parts of finer structure appear darker 

 than those of coarser structure. In the latter, the grains are large enough to show that they all have a uniform reflec- 

 tion and that by weak etching they acquire a smooth surface, and by stronger etching they acquire an uneven and 

 therefore less lustrous surface. The dark network may, from its appearance, be composed of nickel-iron richer in car- 

 bon than that of the grains; however, it can scarcely be an iron carbide of the composition of cohenite, since the 

 analysis gave a carbon content of only 0.06 per cent. 



Since the structure is not composed of lamellae of different composition, we can not speak of a normal octahedrite. 

 But it is, nevertheless, very apparent that the faintly defined edges of the particles, which are distinguished by color 

 and size, are actually, as Brezina conjectured, oriented according to the octahedral surfaces. In a specimen which I 

 examined, having two sides perpendicular to one another, every portion intersects its fellow nearly at right angles, and 

 then the ensuing figure resembles that of an octahedrite sectioned parallel to a hexahedral face; in other places, however, 

 they seem to be oriented irregularly to one another. As in the case of Cacaria the structure may be best described as an 

 individually streaked one. 



Schreibersite is abundant and occurs in various forms, but is more abundant in the more coarsely constructed 

 portions. Here one meets with small scales or grains up to 0,25 mm. in size, which are occasionally arranged in straight 

 lines. Large, irregular individuals are fewer in number; in the case of the longer forms they arrange themselves in aggre- 

 gations of from 1.5 to 2 cm. in length so that the crystals remain perpendicular to a more or less bent axis. Such a 

 feather-shaped formation I have nowhere else observed in meteoric iron. The schreibersite is without exception 

 surrounded by a broad, dark, very fine-grained envelope which appears to be identical with the above-mentioned dark 

 border of the fieldlike particles. In this border there is, in connection with the larger individuals and the aggregations 

 in their totality, a broad zone of somewhat coarser grain and therefore of lighter color than the rest of the nickel iron, 

 since the size of the grains is from 0. 05 to 0. 15 mm. The tolerably frequent elongated, irregularly bounded cavities 

 are due to the weathering out of feather-shaped aggregations of schreibersite such as may often be seen in the still 

 remaining residue. Brezina's observation of troilite intermingled \pth schreibersite I was unable to verify. 



Hammond appears still to possess the original fusion crust, although it is almost completely altered to iron hydroxide. 

 That no considerable portion of the nickel iron has scaled off is indicated by the presenc,e of the 1.5 to 2.5 mm. wide 

 alteration zone which shows up distinctly immediately upon weak etching. It compares in color and grain with the 

 dark streaks. 



It is noteworthy that two section surfaces on the same piece at right angles to each other each take a different polish. 

 One becomes quite even and of a uniformly bright luster; the other uneven, on account of numerous small pitting?, so 

 that it appears as if covered with pin pricks. Their origin can not be determined with certainty, but I think that they 

 are due to the breaking out of small particles of schreibersite in the process of polishing. If this is the case it would 

 indicate a definite orientation of the schreibersite particles. 



Analysis by Fahrenhorst: 



Fe Ni Co Cu Or C P S Cl 



91.62 7.34 1.01 0.04 0.01 0.06 0.52 0.01 0.01 =100.62 



Composition : 



Nickel-iron 96. 59 



Schreibersite 3. 36 



Daubreelite 0. 03 



Lawrencite 0. 02 



The variable and always low specific gravity (7.288-7.506) can be accounted for only by the supposition that there 

 were cavities in the interior of the piece. 



The meteorite is almost wholly (23,640 grams) preserved in the Yale collection. 



BIBLIOGRAPHY. 



1. 1887: FISHER and KUNZ. Description of an iron meteorite from St. Croix County, Wisconsin. Amer. Journ. 



Sci., 3d ser., vol. 34, pp. 381-383. (Illustration of the iron, an etching, and an analysis.) 



2. 1893: BREZINA. TJeber neuere Meteoriten (Nurnberg), p. 166. 



3. 1895: BREZINA. Wiener Sammlung, p. 289. 



4. 1900: COHEN. Meteoreisenstudien XI. Ann. K. K. Naturhist. Hofmus. Wien, Bd. 15, pp. 355-359. 



5. 1904: KLEIN. Berlin Sammlung. Sitzber. Berlin Akad., p. 151. 



6. 1905: COHEN. Meteoritenkunde, Heft 3, pp. 406-410. 



