F. JV. Guild — Eruptive Rocks in Mexico. 165 



< — ]>r-* Class II, Dosalane 



Sal __ 81-83 7 .5 



Fern" 18-16 ' < 1 ^3 



Q 13-08 ' 3 "* 1 - + 



^ = , <T — > — , Order 4, Anstrare 



F 67-85 ' /"■ 5. 7 ' 



KO+NaO 89 ^ 5 . 3 _ o _ . 



' T ' — = ^— , < - >- i Rang 3, Tonalase 

 CaO 74 ' ^ 3 - 5 ' 5 ' 



^ 2 ^ =r — , <-"> — , oubranff 4, lonalose 

 Na 2 69 ' > 5 ^ 7 ' & ' 



.No. 3. 



Quartz, Si0 2 8*88$ 



Orthoclase, K a O. AI a 8 .6Si0 2 10-01 



Albite, Na 2 0. Al 2 3 .6Si0 2 32-49 



Anorthite, CaO. Al 2 3 .2Si0 2 20'85 



( CaO.Si0 2 ' 4-52 ) 



Diopside -i FeO.SiO, '66 [ 8-58 



( MgO.Si0 2 3-40 ) 



Hypersthene { f^MoJ ^-l 1 } 12M 



Magnetite, FeO.Fe 2 3 .._ 4-18 



Ilmenite, FeO.Ti0 2 2-28 



Apatite . _ _ '62 



Rest -59 



Sal 72-23 7 . 5 7T 



ts — = , <C — J> — , Class 11, 



Fem 28 17 ' > 1 ^ 3 ' ' 



100-99 

 Dosalane 



Q 8-88 3 _ . t "j Austrare 



T = 63^36" '< 5 ' ° rder 4 "° ( Gernianare 



K 2 + Na 80 ^5^ 3 „ n (Tonalase 



_ CaO 



= 75' < 3 > 5 ' Rang 3 \ Andase 



KO 18 3^ 1 ■ „ _ , \ Tonalose 



Wzfi = 62 ' < o> 1 ' Submng 4 \ Andose 



Sierra de Guadalupe. 



The regularity of the valley of Mexico is broken in many 

 places by branches extending from the high mountain ranges 

 and reaching in some cases almost to the city of Mexico. One 

 of the most conspicuous of these is the Sierra de Guadalupe 

 located directly north of the city, and consisting of a series of 

 rounded hills of low altitude (fig. 3). The three elevations 

 nearest the city of Guadalupe are known as Cerro de Guerrero, 

 Cerro de San Isabel and Cerro de Chiquihuite. At the base, 



