METEORITES OF NORTH AMERICA. 415 



characteristics. The piece showed polar magnetism, and after magnetization with a strong electromagnet it showed 

 a specific magnetism of 5.7 absolute units per gram, which, considering the unfavorable shape of the section, answers 

 to a pretty considerable permanent magnetism. Therefore, the mass may not have been subjected to a very high 

 degree of heat. As already pointed out by Brezina, the special characteristics of the Shingle Springs iron are the 

 bright etching specks and the great abundance of rhabdite ; in addition to this is the high percentage of nickel. These 

 three characteristics are not combined in the same degree in any other meteoric iron. 



The rhabdite needles appear to be uniformly distributed throughout the entire iron and are irregularly oriented. 

 By far the greater number are of diminutive size, about 0.03 to 0.07 mm. long and 0.003 to 0.006 mm. thick; a small 

 number attain a length of 1 to 1.5 mm. and a thickness of 0.1 to 0.2 mm., and only one needle was observed 5 mm. in 

 length by 0.15 mm. in thickness. Under a stronger magnifying power many present the appearance of rods bounded 

 by straight lines, others are variously bent, as if they were corroded. Schreibersite is found only in one place in small 

 irregularly formed particles. 



The bright, strongly reflecting etching spots are irregularly bounded although mostly elongated and then arranged 

 nearly parallel with the longer axis; on the edge toward the dull portions it often branches out into brushlike rami- 

 fications and finally breaks up into small isolated points. There is no gradual transition; the border appears always 

 distinct when the etched surface is examined in the proper position with reference to the direction of the light. 

 Under a stronger magnifying power diminutive strongly reflecting points and streaks may be seen, which are sharply 

 marked off from the surrounding dull ground; they occur in large numbers in the interior of the brighter etching 

 points, but much less abundantly in the darker portions. There may be etch pits present. Therefore, it may be 

 said that by the proper turning of the plate with reference to the direction of the light a position may be found in 

 which the boundaries of the lighter and darker portions entirely disappear. Then the entire section, omitting the 

 rhabdite, appears uniform and perfectly dense; no indication whatever of a granular structure is to be seen even by 

 strong magnifying powers. The existence of a crystalline structure is self-evident, however, when one considers the 

 occurrence of etch pittings which reflect the light in certain positions. 



The phenomena observed can only be explained by means of a sort of streaked structure, such that the streaks 

 are. less compact and are less readily attacked by the acid than the rest of the nickel iron. Upon the former arise, 

 therefore, more readily and in greater number the etch pittings which occasion the bright sheen in reflected light. 

 The difference in structure by which the different behavior in the presence of different etching agents arises is, how 

 ever, so insignificant that it can only be detected in this manner. 



Both on account of the high percentage of nickel and the occurrence of the etching spots (in places the etching 

 bands), Shingle Springs is closely related with the Cape, Iquique, and Kokomo irons; according to the description 

 of Kunz and Weinschenk, .Ternera may also be included here. If no especial weight be given to the kind of edging 

 of the bright portions, this meteoric iron may be included in a well-defined group with the following common char- 

 acteristics: High percentage of nickel; bright etching bands and spots; dense structure of the nickel iron. Such a 

 grouping appears to me more natural than the division into two groups by Brezina. The latter unites the Cape, Iqui- 

 que, and Kokomo irons in the Cape iron group, and arranges Shingle Springs and Kokomo under the Chesterville 

 group, which, in consequence of this, acquires quite a heterogenous composition. 



The principal portion of the meteorite seems to be lost. Willfing I0 lists the distribution of 

 only 1,650 grams, of which the Yale collection possesses the largest amount (932 grams). 

 Prof. H. A. Ward has informed the writer that the principal mass fell into the hands of boys 

 shortly after its description by Shepard and was lost. 



BIBLIOGRAPHY. 



1. 1872: Shepard. On a meteoric iron lately found in Eldorado County, California. Amer. Joum. Sci., 3d ser., 



vol. 3, p. 438. (Analysis.) 



2. 1872: Jackson. Analysis of the meteoric iron of Los Angeles, California. Idem, 3d ser., vol. 4, pp. 495-496. 



(Analysis.) 



3. 1873: Silliman. On the meteoric iron found near Shingle Springs, Eldorado County, California. Idem, 3d ser., 



vol. 6, pp. 18-22. (Analysis and illustration.) 



4. 1874: Smith. Idem, 3d ser., vol. 6, p. 392. 



5. 1876: Wright. On the gases contained in meteorites. Idem, 3d ser., vol. 11, pp. 2.56 and 257; and vol. 12, p. 167. 



6. 1887: Flight. Meteorites, pp. 12-13. 



7. 1893: Brezina. Ueberneuere Meteoriten (Nurnberg), p. 166. 



8. 1893: Meunier. Revision des fers m6t<k>riques, p. 75. 



9. 1895: Brezina. Wiener Sammlung, p. 294. 



10. 1897: Wulfing. Die Meteoriten in Sammlungen, pp. 325-326. 



11. 1899: Cohen. Meteoreisenstudien IX. Ann. K. K. Naturhist. Hofmus. Wien, Bd. 13, pp. 477-481 



12. 1905: Cohen. Meteoritenkunde, Heft 3, pp. 156-161. 



Sibley County. See Arlington. 



Sierra de las Adargas. See Adargas. 



Signet Iron. See Tucson. 



