184 



INTRODUCTION TO GENERAL SCIENCE 



under proper conditions, the waves pile up deposits and pro- 

 duce new land. The waves work their way through rocks, 

 forming caves and caverns. The water wears away the softer 

 parts of the rocks, and does not affect the harder parts as 

 much. 



Wind Erosion. 



Sea Erosion. 



Wind Work on Deserts. 



Wave and Tide Work. 



Action of W.'nd. 



Wind Erosion. 



Force and Work of Waves. 



Wind Erosion. 



Wave Action. 



Wind Action in Deserts. 



Work of the Sea on the Shore. 



Ocean Erosion. 



Surface Effect of Winds. 



The Work of the Wind. 



Erosion by Waves. 



Shore Erosion. 



131. DISINTEGRATION DUE TO PLANT AND ANIMAL LIFE 

 BACTERIA 



We are continually learning more about the effect of bac- 

 teria on all the changes which take place in matter. We know 

 that they play a great part in the disintegration of rock and 

 soil material, forming plant food in which vegetables may have 

 their life. Bacteria aid in many chemical changes, especially 

 those of decomposition, and probably aid in chemical reactions 

 to a considerable extent. Later we will take up the study of 

 bacteria under various headings. 



