214 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 



on the shale ball having an iron center, and none in that of the shale 

 found on the plains. Farrington, combining his analysis, finds 42.39 

 per cent of magnetite, basing his figures upon the assumption that 

 the protoxides of iron and nickel are so combined, and thus account- 

 ing for the magnetic character of the shale. I find no protoxide of 

 iron in "C," and therefore have no reason for assuming the presence 

 of magnetite in that case, at least. I am inclined to regard the iron 

 shale as being made up essentially of limonite with some turgite, 

 basing my opinion upon the physical characters of the shale in pref- 

 erence to data derived from combining the results of the analyses — a 

 method admittedly speculative. Further, in the portions analyzed by 

 me the magnetic character of the material is certainly due in part at 

 least to the relatively large amount of unaltered schreibersite present 

 and which is plainly visible in many sections of the iron shale. 



