390 



Index 



geysers and volcanoes, no; absorp- 

 tion of light by, 169-170; as con- 

 ductor of electricity, 216; use of, 

 for generating electricity, 256-257; 

 softening due to, 290-292 ; elements 

 of, 294-297 ; a compound and not a 

 mixture, 308; formed by burning 

 fuel, 316; why fire is put out by, 

 but not burning oil, 317 ; combining 

 of carbon dioxid and, by plants, 

 332-333; rusting of iron by, 349; 

 acids and bases turned to salt and, 

 by combining, 361-362. 



Wear, a result of friction, 53. 



Weather, forecasting of, 282-285. 



Weight, center of, 30-33*. 



Wet battery, 204-205*. 



White, a combination of all colors, 162. 

 Winds, cause of, 20-21. 

 Winter, reason for cold in, 127-128. 

 Wiring for arc lamps, 236-239. 

 Wood, poor conductor of heat, 118; 

 carbon and hydrogen in, 315. 



Yardstick, experiment with, to show 



leverage, 59*-6o. 



Yeast, action of, in bread making, 365. 

 Yellow, in flames, 318. 

 Yerkes Observatory, telescope of, 



156*. 



Zinc, in electric battery, 203-206; 

 an element, 300 ; used for driving 

 hydrogen out of acid, 301, 304. 



