METEORITES OF NORTH AMERICA. 



197 



" Calculated to 100 per cent. 



b Minus 6.01 FeO, equivalent to 4.67 Fe, required by S to form FeS (troilite). 



Minus 2.67 S to form FeS (troilite). 



The approximate composition of the mass was got by extracting everything possible by an electromagnet, which 

 took out all the nickel iron and a little troilite, leaving the siliceous part and most of the troilite. Then the amount of 

 S present in the magnetic portion and that in the siliceous portion was calculated as FeS, the silicates were split into 

 two portions by HC1, and by the weights found in each case the given approximate composition was calculated. Under 

 the head of analysis of nickeliferous iron is given the analysis of the metallic portion after allowing for a very slight 

 amount of attached silicates and troilite. 



The analyses numbered from 1 to 5 are the residue left after removing all the magnetic material. Column 1 is the 

 part soluble in HO, column 4 that insoluble in HO; these two added together would give the analysis as a whole of the 

 nonmagnetic portion. Column 2 is the same analysis as 1, after removing the 2.67 per cent S and an amount (6.01 

 per cent) of FeO equivalent to the Fe necessary to form troilite with the S. Column 3 is the same as 2 calculated to 

 100 per cent. Column 4, as stated, is the analysis of the insoluble portion and 5 is the same to 100 per cent. It is of 

 course probable that the Cr 2 3 represents chromite, and possible that the alkalies and alumina with a Little lime repre- 

 sent a soda-lime feldspar. 



In 1891, Torrey and Barbour 4 published a further account of the fall, as follows: 



The Winnebago County meteorite fell near the new town of Thompson, 11 miles northwest of Forest City, Win- 

 nebago County, at 5.15 p. m., May 2, 1890. Seven large fragments are noted, weighing, respectively, 86 pounds, 66 

 pounds, 10 pounds, 10 pounds, CO ounces, and 60 ounces, and, according to Prof. N. H. Winchell , about 5,000 small 

 fragments weighing from the fraction of an ounce to a pound or more. Between two and three hundred small frag- 

 ments are in the collection of Yale University alone. About 100 pieces and the 66-pound piece are in the University 

 of Minnesota. Others are owned by Ward and Howell, Rochester, New York, and by Geo. F. Kunz, New York City. 



The dead-black, scoriaceous crust, when broken, reveals a light gray stone interspersed with innumerable dark 

 particles of iron, and globules of troilite, quite like the Iowa County stones in appearance. Thin seams and cracks 

 occur occasionally filled with a substance that has somewhat the appearance of graphite, and small spheroidal masses 

 of olivine are abundant. The specific gravity is 3.638. 



Chemical composition of the matrix from a fragment of the 66-pound aerolite: 



Si0 2 

 47. 03 



Fe 2 3 



29.43 



A1 2 3 

 2.94 



CaO 



17.58 



MgO 



2.96 



= 99.94 



This is but the approximate composition, and it is our opinion that nothing else should be offered, and that no 

 analysis yet published is strictly reliable, owing to the nonhomogeneous character of the matrix. Another difficulty 

 not sufficiently recognized is the practical impossibility of separating the iron from the matrix by the magnet, owing 

 to the infinitesimal division of the iron, which is still visible under the microscope, even in the impalpable powder. 



A partial analysis of the metallic portion gave: 



C Mn S P 



=99. 93 



The so-called 104-pound fragment or "Kossuth County aerolite " deserves notice here from the fact that it figured 

 in all the earlier notices, at least, as the largest fragment of the Winnebago County meteorite, being sold to parties in 

 Forest City as such, whereas it is simply a fraud. Pieces of the bowlder commonly called "nigger head" were sent 

 us at once for examination. Analysis showed it to be a diorite or allied rock, without crust ; no metal present. Gravity 

 (2.83) about one unit lower than that of the meteorite. 



