CONTENTS. ix 



Humid Climates, 162. Subsoils in the Arid Region, 163. Deep Plow- 

 ing and Subsoiling in the Arid Region ; examples of Plant growth 

 on Subsoils, 164. Resistance to Drought, 167. Root System in the 

 Humid Region, 168. Figures of the Root System of an Eastern (Wis- 

 consin) Fruit Tree, 168. Comparison of Root Development in the 

 Arid and Humid Regions, 169. Prune on Peach Root, 169. Adapta- 

 tion of Humid Species to Arid Conditions, 169. Grapes, 170. Ken- 

 tucky and California Maize, 175, 176. Hops, 172. Deep Rooting in the 

 Arid Region, 174. Goose Foot and Figwort, 174. Importance oj 

 Proper Substrata in the Arid Region, 175. Injury from Impervious 

 Substrata. Figure, 177. Faulty Lands of California. Figure, 178. 

 Shattering of Dense Substrata by Dynamite, 181. Leachy Substrata, 

 182. "Going-back" of Orchards, 182. Hardpan, Formation and 

 Varieties, 183. Nature of the Hardpan Cements, 184. Bog Ore, Moor- 

 bedpan and Ortstein ; Calcareous and Alkali Hardpan, 184. The Causes 

 of Hardpan, 185. " Plowsole," 186. Marly Substrata, 186. 



CHAPTER XI. 



THE WATER OF SOILS. HYGROSCOPIC AND CAPILLARY MOISTURE, 188. 

 General Properties, 1 88. Physical Factors of \Vater compared with 

 other Substances. Table, 188. Capillarity or Surface Tension, 189. 

 Heat Relations, 190. Density, 190. Specific Heat and its Effects, 190. 

 Ice, 191. Vaporization, 191. Solvent Power, 191. Water-requirements 

 of Growing Plants, 192. Evaporation from Plants in Different Climates, 

 192. Relations between Evaporation and Plant Growth. Table, 193. 

 Fortier's Experiments. Figure, 194. Different Conditions of Soil 

 Water, 196. Hygroscopic Water in Soils ; Table, 196. Influence of 

 Temperature and Air-Saturation, 197. Utility of Hygroscopic Water 

 to Plant Growth, 199. Mayer's Experiments, 200. Summary, 200. 

 Capillary Water, 201. Ascent of Water in Soil-Columns. Table, 202. 

 Ascent in Uniform Sediments. Figure, 204. Maximum and Minimum 

 Water-holding Power, 207. Capillary Water held at different Heights 

 in a Soil Column. Table, 208. Capillary Action in Moist Soils, 210. 

 Proportion of Soil Moisture Available to Plants, 211. Moisture Require- 

 ments of Crops in the Arid Region, 211. Tables of Observations in 

 California, 214. 



CHAPTER XII. 



SURFACE, HYDROSTATIC AND GROUND WATER. PERCOLATION, 215. 

 Amount of Rainfall, 215. Natural Disposition of Rain Water, 216. 

 The Surface Runoff, 216. Washing-away and Gullying in the Cotton 

 States, 217. Injury in the Arid Regions, 219. Deforestation, 219. 

 Prevention of Injury to Cultivated Lands from Excessive Riinoff, 220. 

 Absorption and Movements of Water in Soils, 221. Determination of 

 Rate of Percolation. Diagram, 221. Summary, 224. Influence of Var- 

 iety of Grain-sizes, 224. Table of King's Experiments, 224. Percola- 

 tion in Natural Soils. Figure, 225. Ground or Bottom \Vater, 227. 

 Lysimeters, Surface of Ground Water ; Variations, 227. Depth of 



