XIV CONTENTS 



SECTION PACK 



110. Home-made Weather Instruments ..... 150 



111. The Ocean 150 



112. Purification of Water 152 



113. Springs and Streams 155 



114. Composition of Water 156 



115. Solution and its Effects . . . . . .157 



116. Uses of Water 160 



117. Surface Tension 162 



118. Capillarity 164 



119. Osmosis 166 



120. Removal of Grease Spots and Stains 168 



121. Acids, Bases, and Salts Neutralization . ... 170 



122. Hygroscopic and Efflorescent Salts ..... 173 



123. Soap " . 174 



124. Hard Water 176 



125. The Earth's Crust 177 



126. Changes in the Surface of the Earth 178 



127. Weathering and the Rate of Weathering . . . .179 



128. Agents of Weathering . . . . . . .180 



129. Erosion . .182 



130. Agents of Erosion . . . . .... . . 183 



131. Disintegration Due to Plant and Animal Life Bacteria . 184 



132. Slowness of Change . .185 



133. Rocks Defined and Classified 186 



134. The Difference between Minerals and Rocks . . ,187 



135. Rocks of the Earth's Crust . . .. . . . .188 



136. Organic Rocks . . . . , : . . . .191 



137. Coal, Soft and Hard . 192 



138. Petroleum and Natural Gas . 194 



139. How Mountains are Made ... . . . . 195 



140. The Source of Food The Soil 196 



141. The Farm a Workshop 197 



142. Resources of the Soil 199 



143. Kinds of Soil . . 200 



144. Transportation of Soils 201 



145. Texture of the Soil ..202 



146. Importance of Moisture 204 



147. How Water is Held in the Soil 205 



148. To Increase the Moisture-holding Capacity Tilling . 206 



