GEO

 CHEMICAL COMPOSITION
 The chemical analyses of some of the rocks described in the preceding paragraphs are included in MacDonald's manuscript. As noted in the explanatory matter following the table of analyses, they have already been published in the Geological Survey's Bulletin 591. Missing pages of the manuscript may contain descriptions of the "andesitic rock near Empire" and the 'lava near Las Cascadas", analyses of which were published


in Bulletin 591. The norms of the analyzed rocks were calculated by MacDonald.
 Some abnormalities in mineralogical composition resulting from various degrees of albitization probably account for the high soda and low lime content of some of the rocks, particularly the dacites (analyses 3, 6). The low potash content is typical of many similar rocks in the Caribbean region.


 Analyses of igneous rocks and tuff from Canal Zone [Analysts: 1, 2, 6, 7, R. C. Wells; 3, 8, George Steiger; 4, 5, W. C. Whmeler]

 Granular intrusive rocks Dike rock


Si02 -A20 -FeG0
Feo
A1g0 -- CaO -N120 K20 _ H20 -- 
H20- -Ti 2-C02 -- --P205 -_- 

Cl -_ _. S _--- _----C r20 3_ _-_--_-MnO ----BaO---__- 

 Total-


 63. 51 18. 07 2. 01 2. 18 2. 19 5. 14 4. 08 88 1. 07
 .60 33
 None
 19
-----_- 
 .01 .01

 06 03

 100. 36


57. 39 69. 20 15. 84 15. 00 2. 38 1. 57 5. 96 1. 83 2. 41 69 5.24 1. 88 5. 23 5. 87 84 1. 81 1. 09 .90 1. 74 .67 1. 35 .52
Trace None .68 .10

 .05 
 .01
 _-------_.18 15
 .02 --100. 41 100. 19


51. 72 15. 38 3. 35 7. 91 4. 38 7. 84 4. 37 .47 .56
 2. 00 1. 67
 None .49 03
 12

 None 16


100. 45


 5


 48. 23 14. 69 4. 49 5. 85 6. 73
 12. 12 2. 55 1. 49 1. 50 .98 1. 00
 Trace 46 05 09

 06 17


100. 46


 Volcanic rocks and tuIf

 6 7 62. 23 65. 17


 15. 22 2. 08 3. 98 1. 19 3. 79 3. 71 1. 52 2. 57

 96 32






 06


100. 57


14. 95 2. 04 1. 52 75 3. 10 5. 08 1. 26 8. 94 59
Trace 04


100. 50


8


51. 04 17. 34 2. 88 7. 33 5. 50 9. 79 2. 88 .53 96 72 1. 32
None
 25


 13


100. 67


 I Shows a trace Of V203. 2 Shows traces of Zro02, F, and V2.

 1. Quartz diorito porphyry, Cocovi Island, Panan Bay. Clarke, F. IV., Analyses 5. Basalt, Panamna Railroad, 3 ki northwest of Mtonte Lirio. Bull. 591, p. 214, of rocks and minerals from the laboratory of the U. S. Geol. Survey. U. S. Geol. analysis Q. Survey Bull. 591, p. 214, 1915, analysis 0. 6. Dacitic glassy lava in Las Cascadas agglomerate, Gaillard Cut. Bull. 591, p. 213,
 2. Augite quartz diorite, Point Farfan. 1ull. 591, p. 214, analysis N. analysis E.
 3. Dacatic, Ancon 5ill. Bull. 591, p. 213, analysis A. 7. Dacitic tuff in Cucaracha formation, Gaillard Cut. Bull. 591, p. 213, analysis B.
 4. Diorite, Point Farfan. Bull. 591, p. 214, analysis P. 8. Basalt capping Gold Hill, Gaillard Cut. Bull. 591, p. 213, analysis G.


55


LOGY


22


f
1