Index 



Ocean, why salt, 104-105. 



Oil, reason for floating of, 26-27 ; 

 decreasing of friction by, 53-54; 

 softening due to, 290-292 ; carbon 

 and hydrogen in crude, 315; why- 

 water will not put out burning, 317. 



Oil heaters, action of, 319. 



Orange, litmus test of, 359. 



Osmosis, process called, 272-274. 



Osmotic pressure, 272-273*. 



Oxidation, 312-322. 



Oxygen, an element, 293, 299; an 

 element of water, 295-296; experi- 

 ments in getting, from two solids, 

 305-308*; function of, in burning, 

 308 ; part taken by, in burning 

 (oxidation), 312-313; released in 

 manufacture of plant food, 333-335 ; 

 a compound of, an essential in ex- 

 plosives, 347. 



Pancakes, made from sour milk, 362. 

 Paper, carbon and hydrogen in, 315. 

 Paraffine, production of, 114. 

 Parallel circuits, 221-223*. 

 Peat, carbon and hydrogen in, 315. 

 Pencils, making arc light with, 233*- 



234*. 



Periscope experiment, 134-135*. 

 Petroleum, gasoline and kerosene 



distilled from, 114. 

 Phonograph, working of, 177-178*. 

 Phosphorescence, cause of, 341-342. 

 Phosphorus, an element, 300 ; meaning 



of name, 341. 

 Photographs, process of making, 327- 



332*. 

 Pitch of sound, explanation of, 185- 



188*. 

 Plants, light and the manufacture of 



food in, 332-333; how oxygen is 



supplied by, 333~33S- 

 Plating of metals, 336-339*. 

 Platinum, an element, 300. 

 Poles, positive and negative, 206-207. 

 Porcelain, used as insulator, 215. 

 Positive charges of electricity, 198-200. 

 Potassium, experiment with, 304. 

 Potassium chlorate, an essential in 



explosives, 347. 



Precious stones, formation of, 263-264. 



Prism, refraction of light by, 136- 

 140*; separation of light into rain- 

 bow colors by, 162-163*. 



Quicksilver. See Mercury. 



Radiation of heat and light, 122*- 



128. 



Radium, an element, 300. 

 Rain, 275 ; cause of, 278-280. 

 Rainbow, making a, on wall, 162*- 



163; how formed, 170-171. 

 Reading glasses, 144*; convex lens 



in, 150. 

 Red color of sky at sunset, reason for, 



170. 



Reflecting telescopes, 157. 

 Reflection of light, 129-135*. 

 Refraction of light, 136-141*. 

 Resistance, electrical, 229-232. 

 Retina of eye, 151*, 153. 

 Reverberation of sound, 183-185. 

 Ring around moon, cause of, 131. 

 Rock candy, how made, 267. 

 Rubber, used as insulator, 215. 

 Rusting of iron, 349. 



Safety valves on steam boilers, 347. 



Salt, reason for, in sea, 104-105*; 

 a compound, 308; elements of, 310- 

 311; formed by hydrochloric acid 

 and zinc, 351 ; iron, formed by lemon 

 juice on steel, 353 ; acids and bases 

 turned to water and, by combining, 

 361-362. 



Salt water, litmus test of, 359. 



Samson cells, 204. 



Scattering of light (diffusion), 158- 

 161*. 



Seesaw, example of a lever, 57-58*. 



Seltzer siphon, working of, 17. 



Ships, reason for floating, 24*-26. 



Shock, electrical, 214-215. 



Short circuits and fuses, 240-245. 



Silver, an element, 300; plating of, 

 339 ; hydrochloric acid test for, 373. 



Silver chlorid, formation of, 327. 



Sinking and floating, 23-28*. 



Siphon, 1 8*. 



