CODSTTEISTTS. 



CHAPTEE I. 



Page. 

 General considerations relating to the topography and geological history op the 

 High Plateaus and their relations to the Plateau Province of which they form 



A I ART 1 



Situation of the High Plateaus. — The several ranges and intervening valleys. — Relations of High 

 Plateaus to the Plateau Province at large. — Geological history of the province. — Its lacustrine 

 strata. — Its emergence and desiccation. — Its erosion. — Its drainage system. — Origin of its 

 peculiar features. 1-24. 



CHAPTEE II. 



Structural geology of the High Plateaus 25 



Faults and monoclinal flexures. — The principal faults described. — A discussion of their age. — 

 Ancient displacements. — Parallelism of faults to the ancient shore line. — A comparison of 

 the structural forms prevailing in the Park, Plateau, and Basin Provinces. 25-54. 



CHAPTEE III. 



Volcanic phenomena presented in the district and a general discussion of them 55 



Initial epochs of eruption. — Order of succession of eruptions. — Richthofen's law of succession. — 

 Fragmental volcanic rocks. — Tufas. — Volcanic conglomerates. — Origin of the clastic beds. — 

 Metamorphism of tufas. 55-81. 



CHAPTEE IV. 



CLA SSIFICATION OF THE VOLCANIC ROCKS 82 



A discussion of principles of classification and the objects to be gained. — Classification primarily 

 in accordance with chemical constitution. — Correlations between chemical constitution on 

 the one hand and mineral and physical constitution on the other. — Lithologieal texture. — 

 Correlation between texture and geological age. — Von Cotta's view adopted. — The porphy- 

 ritic texture. — Acid and basic rocks. — Subdivisions — rhyolite, trachyte, andesite, basalt. 

 82-112. 



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