360 



OUR PHYSICAL WORLD 



Derrick, 346 



Detector, 256, 257, 264; crystal, 257; 

 vacuum tube, 268, 269 



Developers, 316, 317; making up, 318 



Developing, directions for, 319 



Devil's Pile Quarry, 69 



Diabase, 66, 69 



Diamond, 50, 51, 247 



Diana, n, 33, 34 



Diaphragm, 303, 311, 314; openings, 

 sizes of, 311 



Diorite, 66, 68; porphyry, 66, 69 



Dipper, Big, 19, 20, 38, 39; Little, 22 



Dispersion of light, 304 



Distances, judging, 288 



Distributor, 196 



Dog days, 18 



Dog star, 18 



Dogs, Greater and Lesser, 33, 34 



Dolerite, 66 



Dolomite, 50, 56, 61 



Dolphin, the, 40 



Draco, 25, 26, 28, 29 



Dragon, the, 25, 26, 28, 29 



Drill: compressed air, 144; dentist's, 

 240; fire, 147 



Dry battery, 230 



Dugouts, 1 20 



Du Moncel, 219 



Dynamo, 195, 240; method of opera- 

 tion, 241, 242 



Earth: axis of, 10, 15; crust of, 63; 

 equatorial bulge of, 15; North Pole 

 of, 10, 16; orbit of, 10; size of, 4, 7 



Eccentric, 184 



Echo, 328 



Ecliptic, plane of, 9, 10 



Edison, Thomas, 219, 246 



Electric appliances: bell, 221; buzzer, 

 222; cream separator, 133; dynamo, 

 195, 240; flatiron, 228, 249; heater, 

 228, 249; light, arc, 247; light, 

 incandescent, 246; meter, 228; per- 

 colator, 247, 249; sewing machine, 

 239; telegraph, 211; toaster, 247, 

 249; transformer, 245; vacuum 

 cleaner, 239 



Electric current: alternating, 243, 245; 

 cause of, 223, 224, 226; direct, 242; 



direction of flow of, 223, 242; heat 

 equivalent, horse-power, equivalent 

 of, 228; long-distance transmission 

 of, 243; produced by moving magnet, 

 210 



Electric motor, 233; commercial, 234; 

 directions for making, 233; explana- 

 tion of action of, 234, 237; simple, 

 233; toy, 236, 237 



Electric: pressure, 225, 227; repulsion, 

 203, 208; resistance, 225, 229 



Electric wiring of house, 247, 248 



Electrical attraction and repulsion, 

 203, 208 



Electricity: early knowledge of, 202; 

 frictional, 203, 204; galvanic, 205, 

 206; positive and negative, 204; 

 resinous, 204, vitreous, 204 



Electromagnet, 209, 236; winding of, 

 238 



Electron, 165 



Elements: chemical, 145, 165; dis- 

 covery of, 173; names of, 170, 171, 

 176; nature of, 166; negative, 168, 

 169; positive, 168, 169; table of, 170; 

 transmutation of, 173 



Elemus, 85 



Ellipse, how to draw, 9 



Elon-quinol, 317 



Emerald, 51 



Engines, 178 



Equinoxes, 10, n; precession of, 15 



Eridanus, 28, 40 



Erosion, 52, 74 



Ether, 250 



Europa, 32 



Expansion by heat, 116 



Exposure, length of, 311, 313, 314, 322 



Exposure meter, method of using, 312 



Eye, structure of, 188, 305 



Faraday, Michael, 210, 240 



Farman, Henri, 94 



Feldspar, 48, 50, 56, 62; characteristics 



of, 56, 57, 62 

 Field, Cyrus W., 215 

 Fife, 331, 332 



Film, photographic, 320, 322 

 Fish, the Southern, 40, 41 

 Fishes, the, 39 



