Water, action in nature, 70-74. amount used daily per person, 181. and hydrogen, 79. and oxygen, 79, 80. as solvent, 70-71. boiling, 77. boiling point, 15. composition, 79-80. condensation, 33. dams and reservoirs, 214-216. density, 11. distilled, 34, 77. drinking, 75-77, 195-201. electrolysis, 79-80. evaporation, 33-34. expansion, 9-10, 41-42. filtration, 77. freezing, 40-41. hard, 225. heat of fusion, 40. impurities, 76-77. in atmosphere, 36-38. in food, 75. in human body, 75. in vegetables, 75. influence on climate, 29, 40. irrigation, 193-194. minerals in, 70-71. ocean, 265. power, 176-180. precipitates, 72, 73. pressure, 208-211, 214-216. purification, 77. rain, 225. running, value of, 178-180. source of, 78. steam, 32. waves, 145-147. weight, 208-209, 215. wells, 195-201. wheels, 176-180. work under, 203-205. Water supply, and forests, 216-217. cost, 212-214. of city, 206-212, 217. Watt, 351. Waves, heat, 145-147. light, 145-147. sound, 268, 272-274. water, 145-147. Weather, bureau, 87-91. forecasts, 38-39, 86-88. relation of water to, 29, 40. Weather maps, 89-91. Wedge, and inclined plane, 166. Weight, of air, 86. of water, 208-209, 215. Welding, by electricity, 315. Wells, 195-201. drilled, 199. driven, 196-197. Wheel and axle, 169-171. cogwheels, 170. windlass, 169. Wheelbarrow as lever, 160-161. White light, nature of, 135. Wind instruments, 297-301. Windlass, 169. Windmill, 174-175, 180-182. Winds, 24. Wine, 232, 234. Wood, as source of charcoal, 58. ashes in soap making, 223. in paper making, 219. preservation, 253-254. Wool, bleaching, 241. dyeing, 245-247. Work, 156-186. and steam, 183-184. and water, 176-180. conservation, 174-175. formula, 157. machines, 157-175. unit of, 172-173. waste, 173. Woven designs in cloth, 249. Yeast, 234-236. wild, 235-236. Zinc, in galvanizing iron, 49. in making hydrogen, 80. in voltaic cell, 307-308. PLANT LIFE AND PLANT USES By JOHN GAYLORD COULTER, Ph. D. $1.20