xiv LIST OF ILLUSTRATIONS 



FIGURE PAGE 



27. Feldspar, to Show Cleavage 49 



28. A Zinc Mine 51 



29. Basalt 63 



30. Limestone, Showing Stratification 71 



31. Fossils 72 



32. Entrance to a Coal Mine 75 



CHAPTER III 



33. Diagram of the Decomposition of Forces 80 



34. A Tetrahedral Kite in Flight 83 



35. Besnier's Flight Apparatus . 86 



36. De Bacqueville's Wings for Flight 86 



37. Lillienthal's Glider 88 



38. A Recent French Glider 89 



39. Langley's Aeroplane 93 



40. The Aeroplane Frame 98 



41. Front View of Aeroplane Frame 98 



42. Diagram of the End of the Block from Which Propeller Is Cut . 99 



43. The Aeroplane Complete 101 



44. Front View of Biplane Built by Seventh-Grade Pupils . . 102 



CHAPTER IV 



45. A Military Observation Balloon . 107 



46. A Dirigible Balloon * . . no 



47. Tin Can with Tubes in It to Show Water Pressure . . .113 



48. A Coracle 121 



49. An Old-fashioned Wind Mill 123 



50. A Water-Power Plant 126 



51. Diagram of a Lift Pump 129 



CHAPTER V 



52. The Crossbow 136 



53. An Archer 136 



54. The Catapult . 139 



55. The Flintlock Musket . . . 141 



56. An Old Cannon on Its Wooden Carriage 143 



57. An Air Drill in a Quarry 144 



CHAPTER VI 



58. A Fire Drill 147 



59. Diagram of a Fireplace . . 152 



60. Diagram of a Hot-Water Heating System 1 54 



61. A Fire 156 



