Water, seeks its own level, 6-10; gurgling of, when poured from bottle, 13; experiment with, to show centrifugal force, 73-74; used for making thermometer, 90*-92; expansion of, when frozen, 98; evaporation of, 100-106; action of, in geysers and volcanoes, 110; absorption of light by, 169-170; as conductor 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*-60. 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. * * * * * _CONSERVATION SERIES_ [Illustration] Conservation Reader _By_ HAROLD W. FAIRBANKS, _Ph. D._ _Lecturer, University of California; Geography Supervisor Berkeley Public Schools_ A small book bringing out in a simple and interesting manner the principles of conservation of natural resources has long been wanted, or there has been little on the subject that could be placed in the hands of pupils. It is to answer this need that Fairbanks' CONSERVATION READER has been prepared. The book touches upon every phase of conservation, but it deals at greatest length with saving the soil, the forests, and wild life. It is one of the author's main purposes to arouse a stronger sentiment for preserving what remains of the forests as well as for extending their areas. This is because proper forestation will lessen the danger of floods and of erosion of the soil, and it will encourage the return of the wild creatures that are of so much economic importance and add so much to the joy of life. The matter is presented in an easy narrative style that is calculated to arouse the intelligent interest of children. The text is illustrated with photographs of wild animals, trees, landscapes, and rarely beautiful birds, printed in colors. The subject is timely and the treatment is happy throughout. CONSERVATION READER should be used as a reader or as a book for regular study in every elementary school in the country. _Cloth_, vi + 216 _pages_. _Price $1.40_. WORLD BOOK COMPANY YONKERS-ON-HUDSON, NEW YORK 2126 PRAIRIE AVENUE, CHICAGO [Illustration]