wright-fenner] 



PETEOGEAPHIC STUDY 



91 



the scorige. In both analyses the ferrous iron predominates over 

 the ferric iron; in tliis respect the analyses differ notably from those 

 of the tierras cocidas. 



Two analyses by Dr. E. Herrero Ducloux cited by Col. Antonio A, 

 Romero/ of a "tierra cocida" and an "escoria" from Chapadmalal 

 do not show this relation between the iron oxides. For the sake of 

 comparison these analyses have been expressed in the quantitative 

 system and both found to belong to the same subrang; but in this 

 subrang no analysis of an igneous rock has yet been found to occur. 

 Tliis in itself is indicative of the abnormal character of the rocks. 



CJiemical analysis, of Dr. E. Herrero Ducloux. — 



86. 33 



9.50 



100. 02 



Ratios 



^, Sal 86.33 7 



^1^"" F^=X50>r 1 



„ , Q 45.59 5 3 



Order F^SiHl <3 > 5 - " " ^ 



-D KjO' + Na^O' .0306 3 1 



^^^g CaO- -.-0643<5>7--- ^ 



Q , K2O' .0035 1 



^"^^^^g NaT' = .l)27T<7 ^ 



00. Tierra cocida. Chapadmalal, E. H. Ducloux, analyst, 

 a. Molecular proportions of 00. 



In calculating this analysis, the rules prescribed by the*authors 

 of the quantitative classification for the calculation of the CI were 

 not followed by the writers. This procedure would have indicated 



1 In Anales del Museo Naciojial de Buenos Aires, xxn (set. iil, t. xv), pp. 11-31 (separate, 1911). 



