60 



BUREAU OF AMERICAN ETHNOLOGY 



[bull. 52 



much volcanic material and should express this fact in the chemical 

 analysis. Since some of the tierra cocida specimens are evidently 

 baked loess, it was of interest to have an analysis made of one of 

 the typical loess specimens. This and the following analyses were 

 made by Mr. J, G. Fairchild in the laboratory of the United States 

 Geological Survey : 



42.26 



37.00 



6.63 



85.89 



6.62 



99.98 



Ratios 



^, Sal 85.89 7 j 



^^'^^^ Fem." 6.62>I ^ 



n 1 Q 42.26^5^3 ^ 



^^'^^^^ F = 3T:00<3>5 - --^ 



,, Na,0' + K20' .054^7^5 



^^""''^^^c^' — =:o28<r>3 2 



^ , K^O^ .025^5^3 „ 



^"^^•^^^g Na,O^ = :029<3>5 ^ 



I. Loess, Alvear. J. G. Fairchild, United States Geological 



Survey, analyst. 

 la. Molecular proportions of I. 



In the calculation of this analysis the method used in the quantita- 

 tive system of Cross, Iddings, Pirsson, and Washington has been 

 adopted. This system applies strictly only to fresh igneous rocks 

 and was not intended for use with sedimentary or altered rocks of 

 any description. It is used in the present instance only as a con- 

 venient method for expressing the analysis of a rock which contains 

 an abundance of eruptive material. Characteristic for this rock are 



