INDEX 



429 



Muscles, and bones . . . 370-371 

 how they do work .... 376 



Narcotics 394-398 



Nails, care of 362 



Negative, printing from . . . 147 



making a 146, 147 



Nervous control 386 



Nervous system, care of . 389-391 



fair play to 389 



Nesting boxes 279 



Nests, birds 277 



sunfish 283 



Newton, Sir Isaac 128 



Nicotine 394 



North Star . . . .198, 200, 201 



Nucleus 356 



Nutrient solution for plants . 241 



Oak 271,272 



Observatory, Mount Wilson . 189 



Oil glands 361 



Opaque 135 



Optical illusions 4 



Organism 358 



Organs 357, 358 



Ovary 264 



Oxidation 49 



Oxygen, helps burning . . 48, 49 

 useful and harmful ... 48 



Pasteur, Louis 253, 341 



Pasteurization 341 



Pebbles 215 



Petals 262, 263 



Petri dishes 336, 337 



Phosphorus in body . . . 322, 323 



Photoelectric cell 192 



Photography in astronomy . 190 

 Photographs, how made . 142-147 



Physical change 15 



Pigments, mixing 156 



Pill bug 276 



Pimples, cause of 363 



Pine 271 



Pistil 262,263,264 



Pinhole image, how made . 130, 131 



Plankton 295 



Plants, elements used by . . 242 

 how fitted for work . . . 258 

 mineral substances needed 



for 241 



Poisons, how to treat . . . 407 

 Polaris . . 199, 200, 201, 202, 203 



Porcupine 27 



Positive, making a .... 147 

 Posture, examples of .... 371 



related to shoes 373 



how to get good .... 372 

 value of good .... 371, 372 



Pressure cooker 115 



Priestley 44 



Prism, use of 164 



Problem solving 5 



and the scientist .... 6 



in tennis 6 



Proteins 312, 317, 331 



proportion in diet . . . 331-332 



Quartz 219 



Radiation 110 



Rats, experiments with . . 307-308 

 Recreations depending upon 



water 94, 95 



Refrigeration, electric . . . 343 



iceless 344 



Refrigerator, construction of . 342 



use of . . ' 342 



Rest and health 391 



Rigel 203 



Rocks, from soil 219 



how formed 214 



igneous 216 



metamorphic 217 



sedimentary 217 



Rocks and minerals . . . 217-218 



differences 218-219 



Roots, function of ... 259, 261 



Root hair 261 



Rotation of earth .... 196-197 

 Rusting, causes of .... 47-48 



Safety education, why impor- 

 tant 399, 400 



Salt 218 



Salts, relation to life .... 294 



Sea anemones 296, 300 



Sea urchin 296, 297 



Seaweeds 296,297,300 



Seasonal differences in food re- 

 quirements 330 



Self-testing exercise, use of . . 9 



Sense impressions 4, 5 



Sensory cells 386 



Seeds, how formed .... 260 



how scattered 264 



Sepals 262,263 



Shadow 136 



Shoes, comfortable . . . 373-374 

 Shore, life on 295 



life zones 294 



Signal lights, colored . . . 132 

 Siphon of clam 296, 296 



