CONTENTS. IX 



of the Mineralogical Classifications of rocks, 48, 49. Compared with zoological 

 methods, 49. Question of methods, 50. Earlier publication of these principles, 

 50. European classifications based largely on altered rocks, 50. To express 

 perfectly the Natui-al Classification of rocks requires perfect knowledge of them, 

 50. The classification here introduced empirical, 50, 51. Elasticity of the classi- 

 fication, 51 ; its fundamental principles, 61. 



SECTION YIII. 

 The Principles of Classification 51, 52 



SECTION IX. 



General Conclusions m Regard to Syste.\is of Lithological Classification 53-59 



Universal law of degradation of energy, 53. Natural classification conforms to 

 it, 53. The demands of Petrography, 53. Expansion of materials in passing from 

 the liquid to the solid state, 53. Pressure tends to render the Earth's interior 

 solid, 53. Sinking of the Earth's crust, 53. The structure of the Earth indicated 

 by petrographical and geological facts, 54. Crystalline rocks, 54. Systems of 

 classification, 54, 55. Chemical analyses of rocks, 56. Alteration of rocks, 56. 

 Divisions of minerals and rock fragments in rocks, 56. The order of arrange- 

 ment of rocks, 57. Determination of a rock by means of its unaltered ground- 

 mass, 57. Practical application of the principles of nomenclature and classifi- 

 cation, 57. Specific and varietal names, 57. The use of the terms Melaphyr, 

 Diabase, and Diorite, 57, 58. Sub-varietal names, 58. Trivial names, 68. 

 Arrangement of the fragmental rocks, 58. Arrangement of rock names, 58, 59. 

 Varietal and sub-varietal names not essential, 59. Use of a binomial and 

 trinomial nomenclatui'c, 59. 



CHAPTER II. 



THE SIDEEOLITES AND TALLASITES. 

 SECTION I. 



SiDEROLITE G0-G8 



Definition of Siderolite, GO. Shingle Springs, Eldorado Co., California, 60. 

 Stanton, Virginia, 60, 61. Coahuila, Mexico, 61. Gibbs meteorite, Texas, 61. 

 Butler, Missouri, 61. Toluca, ^Mexico, 61. General structure of meteoric sidero- 

 lites, 61; constituents of, 61. Widmannstiittian figures developed in, 62 ; also in 

 Greenland iron, 62. Eeferences to illustrations of Widmannstiittian figures, 62. 

 Further divisions of the Siderolites, 62 ; chemical analyses of, 62, 63 ; specific 

 gravity of, 63 ; Iron in, 63 ; Nickel and Cobalt in, 63, 64 ; minor elements in, 64. 

 Terrestrial Siderolites, 64, 65. Greenland iron, 65 ; its origin, 65. Doubtful me- 

 teoric origin of many Siderolites, 65. Chemical analysis made sole test of mete- 

 oric origin, 65, 66. Origin of masses of meteoi-ic iron, 66 ; Tschermak's views, 66 ; 



