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CONTENTS. 
Page. 
(2.) Two or more periods__ 85 
— interruption and repetition of the series_ 85 
— essential differences between minerals of the 1st and 2d gen¬ 
eration _ 85 
— essential identity of minerals of the 1st and 2d generation. 86 
— extraneous differences between minerals of the 1st and 2d 
generation, hut identity of mineral species_ 86 
Relation of rock structures to geological occurrence __ 88 
(1.) Geological occurrence of glassy rocks_ 88 
— fine-grained porphyritical rocks_ 88 
— coarsely crystalline rocks_ 88 
(2.) Instances in which the geological location of the magma at the 
time of crystallization can be determined___•_ 88 
Relation of rock structures to chemical composition _ 89 
(1.) Degree or extent of the crystallization_ 89 
(2.) Character of the structure_ 90 
Relation of mineral composition to chemical composition _ 90 
(1.) For rocks of similar geological occurrence_ 90 
(2.) Exceptional relations_ 91 
Relation of mineral composition to geological occurrence __ 92 
Part II. Causes of Crystallization _ 93 
Artificial production of rocks and minerals _ 93 
Researches of Fouque and Levy and others_... 93 
— minerals and rocks produced (basic)_ 93 
— greater tendency of certain minerals to crystallize_ 94 
— minerals and rocks not produced (acid)_1___ 94 
— certain minerals produced by the use of mineralizers_ 94 
Conclusions based upon analogy ___ 95 
— Bunsen’s opinion that rock magmas behave like solutions 
of salts______ 95 
— Lagorio’s views on the same- 95 
— supersaturated solutions_ 95 
— uncertainty regarding the nature of solutions and fusions. 96 
— Sorby’s law applied to rock magmas_ 96 
— changes of temperature and pressure_ 96 
— solubility and saturation_ 96 
— Pelouze’s and others’ experiments on artificial glasses_ 97 
— relative power of saturation possessed by the chemical 
compounds existing in rock magmas_97 
Application of the foregoing conclusions to rock magmas - 98 
(a.) Saturation of rock magmas _ 98 
Its degree dependent primarily on temperature and pressure. 98 
Its character dependent primarily on chemical composition— 98 
Cooling magmas _ 98 
(1.) Order of crystallization and chemical composition_ 98 
(2.) Crystallization under various physical conditions_ 99 
(3.) Comparison with the phenomena of crystallization in rocks. 100 
