March, 1907. Iron Meteorites — Farrington. 



97 



subdivisions may be made of the ataxites, according as they are nickel- 

 poor or nickel-rich. Transitions occur between these, but a general 

 grouping is practicable. Accessory constituents are not usually abun- 

 dant in the ataxites, and when occurring are of small dimensions as a 

 rule. 



A. NICKEL-POOR ATAXITES. 



The nickel-cobalt content lies between 6 and 7 per cent, the com- 

 position thus corresponding to that of kamacite. The structure is, 

 as a rule, plainly granular, seldom compact, the size of the grains 

 reaching 0.75 mm. 



1. SIRATIK GROUP. 



An etched surface appears rough through the presence of irregu- 

 larly arranged depressions, due perhaps to the solution of some acces- 

 sory constituent, such as troilite or schreibersite. The smaller the 

 depressions the more plainly the boundaries of the grains appear. 

 The latter range from 0.33 to 0.75 mm. in dimension. 



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