THE ELEMENTS OF ECONOMIC GEOLOGY 
CHAPTER XV 
PAGE 
THE GEOLOGY OF CEMENTS . . 185 
Definition and Groups of Cements. Hydraulic and Portland 
Cements. Price. Gypsum Cements— Plaster of Paris. 
CHAPTER XVI 
THE SoIL . . 19 
Definition and Function. Soil Constitution—Sand, Clay, and Silt. 
Soil Composition. Soil Texture and Water Capacity. Soil 
Composition and Surveys. 
CHAPTER XVII 
MINERAL FERTILIZERS—NITRATES AND PHOSPHATES . . I 
Nitrates characteristic of Arid Areas. Theories of Formation. 
Phosphates—Value and Use of Phosphorus. Apatite Veins. 
Guano. Rock Phosphates. Lagoon Phosphate. Granular 
Phosphates and Phosphatic Chalk. 
CHAPTER XVIII 
THE SALT DEPOSITS 3 . . 206 
Composition of Sea-water. Concentration in Salt Lakes, The 
German Salt Fields. Intrusive Salt Deposits and Salt 
Domes. Potash Salts—value in Agriculture, Derived from 
Sea-water. Secondary Concentrations. 
ENGINEERING GEOLOGY 
CHAPTER XIX 
PART 1V 
WATER SUPPLY ; . 2I¢ 
Three Sources of Water—Meteoric, Connate, Plutonic or Juvenile, 
Disposal of Rainfall—Run-off, Evaporation, Percolation, 
Circulation of Subterranean Water— Piezometers. The Yield 
of Wells—Water-storage. Wells and Springs. Flowing 
Wells. Rock Pressure. Gas Pressure. Town Supplies and 
Settlement. Reservoir Sites, 
CHAPTER XX 
CoAST DEFENCE, COASTAL WORKS, AND RECLAMATION . . 238 
Waves and Wave Action. Recession of the Land. Transport of 
Beach Material, Continental Shelf. Rate of Marine Abra. 
sion, Coastal Accretion. Warping—the Silting of Estuaries. 
Coastal Protection by Planting and Groynes. Sea Walls, 
Estuary Works and Models.