vi CONTENTS. 



CHAPTER III. 



ROCK- AND SOIL-FORMING MINERALS, 29. Quartz, quartzite, jasper, horn- 

 stone, flint, 29. Solubility of silica in water ; absorption by plants, 30. 

 Silicate Minerals, 31. Feldspars, their Kaolinization, 31. Formation 

 of Clays, 33. Hornblende or Amphibole, Pyroxene or Augite, 33. 

 Their Weathering and its Products, 33. Mica, Muscovite and Biotite, 

 35. Hydromica, Chlorite, 35. Talc and Serpentine ; " Soapstone ", 36. 

 The Zeolites ; Exchange of Bases in Solutions, 36. Importance in 

 Soils, in Rocks, 38. Calcite, Marble, Limestones ; their Origin, 39. 

 Impure Limestones as Soil-Formers, 40. Caves, Sinkholes, Stalactites, 

 Tufa, 41. Dolomite ; Magnesian Limestones as Soil-Formers, 42. 

 Selenite, Gypsum, Land Plaster ; Agricultural Uses, 42. Iron Spar, 

 Limonite, Hematite, Magnetite, 44. Reduction of Ferric Hydrate in 

 Ill-drained Soils, 45. 



CHAPTER IV. 



THE VARIOUS ROCKS AS SOIL- FORMERS, 47. General Classification, 47. 

 Sedimentary, Metamorphic, Eruptive, 47. Sedimentary Rocks ; Lime- 

 stones, Sandstones, Clays, Claystones, Shales, 47. Metamorphic Rocks : 

 Formed from Sedimentary, 48. Igneous or Eruptive Rocks, Basic and 

 Acidic, 49. Generalities Regarding Soils Derived from Various Rocks, 

 49. Variations in Rocks themselves. Accessory Minerals, 50. 

 Granites ; not always True to Name ; Sierra Granites, 51. Gneiss. Mica- 

 schist, 51. Diorites, 51. Diabases, 51. Eruptive Rocks ; Glassy ones 

 Weather Slowly ; Basaltic Oxidize Rapidly, 52. Red Soils of Hawaii, 

 Pacific Northwest, 52. Trachyte Soils ; Light-colored, rich in Potash. 

 Rhyolites generally make Poor Soils, 53. Sedimentary Rocks, 53. 

 Limestones, 53. " A Limestone Country is a Rich Country," 53. 

 Residual Limestone Soils; from "Rotten Limestone" of Mississippi; 

 Table, 54. Shrinkage of Surface, 55. Sandstone Soils, 55. Vary 

 According to Cement, and Nature of Sand, 55. Calcareous, Dolomitic, 

 Ferruginous, Zeolitic, 56 Clay-sandstones, Claystones, 57. Natural 

 Clays, 57. Great Variety, Enumeration and Definition, 58. Colors of 

 Clays, 58, Colloidal Clay, Nature and Properties, 59. Plasticity ; 

 Kaolinite Non-plastic, 59. Causes of Plasticity, 60. Separation of 

 Colloidal Clay, its Properties, 61. Effects of Alkali Carbonates on 

 Clay, 62. 



CHAPTER V. 



THE MINOR MINERAL INGREDIENTS OF SOILS ; MINERAL FERTILIZERS, 63. 

 Minerals Injurious to Agriculture, 63. Minerals used as Fertilizers, 

 63. Apatite; Phosphorites of the U. S., Antilles, Africa, Europe, 63. 

 Phosphatic Iron Ores, " Thomas Slag," 64. Animal Bones ; Composi- 

 tion and 'Agricultural Use, 64 Vivianite, Dufrenite, 65. Chile Salt- 

 peter, 66. Occurrence in Nevada, California, 66. Origin of Nitrate 

 Deposits, 67. Intensity of Nitrification in Arid Climates, 68. Potash 

 Minerals, 68. Feldspars not Available, 68. Depletion of Lands by 

 Manufacture of Potashes, 69. Discovery of Stassfurt Salts, 69. Origin 



