CONTENTS Xlll 



71. Color 98 



72. Refraction and Dispersion 100 



73. The Rainbow 101 



74. Diffusion of Light 102 



75. Twilight 103 



76. Transmission of Light Shadows 104 



77. Eclipses . 104 



78. Measurement of Light 105 



79. Photography 107 



80. The Atmosphere and its Composition 109 



81. Weight of the Air .110 



82. Atmospheric Pressure and the Barometer . . . .112 



83. Boiling from Another Point of View 114 



84. "Suction" 115 



85. Pumps ' . .116 



86. The Siphon 117 



87. Nitrogen and its Uses ........ 118 



88. Effects of Painting Wood Preservation . . . .120 



89. Carbon Dioxide . . . 122 



90. The Chemical Engine 124 



91. Other Constituents of the Atmosphere .... 125 



92. Atmospheric Electricity 126 



93. Warming the Air 127 



94. Winds 128 



95. Kinds of Winds . . . 129 



96. Velocity of Winds . . 130 



97. Resolution of Forces . . . .131 



98. The Theory of the Kite . . . . . . .133 



99. The Theory of the Aeroplane . ... . . .135 



100. Sailing a Boat 137 



101. Humidity 138 



102. Dew ". 139 



103. Frost 141 



104. Fog and Clouds 142 



105. Snow and Hail 143 



106. Rainfall Cyclones 144 



107. Weather Observations 146 



108. Weather and Climate 148 



109. Weather Instruments . ...... 149 



