16 



BULLETIN 149, UNITED STATES NATIONAL MUSEUM 



As may be readily understood, the determination of the chemical 

 mass composition of a stony ii*on is a matter of difficulty. To over- 

 come this so far as relates to the pallasites, Professor Tscherwinsky ^^ 

 resorted to detailed measurements to determine the relative pro- 

 portions of the two essential minerals (olivine and metal), and 

 from the known composition of each, has calculated the average 

 hulk composition of the bodies of which they form the essential part. 

 The percentage by weight of the olivines in the pallasites examined 

 he gives as follows: Admire, 49.69; Ahumada, 46.22; Brahin, 37.18; 

 Brenham, 38.71; Eagle Station, 48.29; Finmarken, 61.22; Ilimaes, 

 43.68; Imilac, 49.25; Krasnojarsk, 52.19; Little Miami, 49.07; 

 Lipovsky, 46.49; Marjahlati, 49.88; Molong, 58.16; Mount Dyrring, 

 75.11; Mount Vernon, 58.94; Pavlodar, 62.49; South Bend, 41.40. 

 The average chemical composition of the pallasites as a whole cal- 

 culated as stated is: 



Per cent 



Silica (SiOo) 20. 08 



Ferrous oxide (FeO) 7. 42 



Magnesia (MgO) 23. 41 



Iron (Fe) ^ 43.33 



Nickel (Ni) 4. 91 



Cobalt (Co) . 27 



Total 99.42 



The stony meteorites are likewise variable, particularly in their 

 metal content. They are of a very basic nature as a rule — ^that is, 

 are low in silica. Those highest in this constituent are the achon- 

 dritic varieties consisting largel}^ of pyroxenes and feldspars like that 

 of Cumberland Falls, Ky. The more basic are among the kugel 

 chondrites like those of Felix, Ala., and Jerome, Kans. 



Below are given two analyses illustrative of extremes in basicity 

 and acidity and in the table following an average of 63 analyses of 

 the highest grade obtainable .^^ 



" Bull. Inst. Polytech. Don. Novocherkassk, 1918. 

 " For methods of analysis, see p. 57. 



