203

33. Making electricity flow 203

34. Conduction of electricity 213

35. Complete circuits 219

36. Grounded circuits 225

37. Resistance 229

38. The electric arc 233

39. Short circuits and fuses 240

40. Electromagnets 247

9. MINGLING OF MOLECULES 259

41. Solutions and emulsions 259

42. Crystals 265

43. Diffusion 268

44. Clouds, rain, and dew: Humidity 274

45. Softening due to oil or water 290

10. CHEMICAL CHANGE AND ENERGY 293

46. What things are made of: Elements 293

47. Burning: Oxidation 312

48. Chemical change caused by heat 323

49. Chemical change caused by light 326

50. Chemical change caused by electricity 335

51. Chemical change releases energy 340

52. Explosions 342

11. SOLUTION AND CHEMICAL ACTION 349

53. Chemical change helped by solution 349

54. Acids 351

55. Bases 355

56. Neutralization 360

57. Effervescence 365

12. ANALYSIS 370

58. Analysis 370

APPENDIXES:

A. The Electrical Apparatus 379

B. Construction of the Cigar-box Telegraph 381

INDEX 383

COMMON SCIENCE

CHAPTER ONE

GRAVITATION

SECTION 1. _A real place where things weigh nothing and where there is
no up or down._

Why is it that the oceans do not flow off the earth?
What is gravity?
What is "down," and what is "up"?

There is a place where nothing has weight; where there is