XV 



THE EFFECT OF WATER AND ICE, OF 

 ANIMALS AND PLANTS, AND OF HEAT 

 UPON THE EARTH 



MATERIAL : Pieces of rock containing fossils, coral, slate, and coal, 

 with impressions of plants ; peat ; pictures of a volcano ; pieces of 

 lava. If practicable, take the children to a place where they can 

 collect and observe fossils in their natural position in the rocks. 

 About localities for collecting fossils consult the Geological Keports 

 of your state, write to the nearest high school or to your state 

 geologist. Keview briefly the chapter on " Geological Effect of 

 Water." 



81. We have learned by former observations that run- 

 ning water erodes the rocks and carries the pulverized 

 material into lakes and river valleys and finally into the 

 ocean. A great deal of the soil in the Mississippi basin 

 and on the Atlantic slope has been made in this way. 

 Many large rivers of the world have formed fertile plains 

 and deltas by means of the soil they brought down from 

 the highlands near their sources. This work has been 

 going on since the rivers began to flow, and it is still going 

 on, because we know that all deltas are growing seaward. 

 Many rivers form no deltas, because the material they carry 

 into the sea is taken up by ocean currents and swept into 

 the deep sea, where its accumulation is not observed. What 

 we have said about the transportation of fine soil you can 

 all understand and prove by observation, but it is more 



Note. Arrange with your pupils to make such observations as are 

 calculated to carry on the work they have begun. 

 x 305 



