338 QUESTIONS. 



142. Point out the different modes in which mountains have been 

 made. 



143. Mention the three ways in which valleys have been made. 

 Of what materials are volcanoes constructed ? Give the facts in re- 

 gard to Fusiyama. 



145. Indicate the mode of formation of volcanic cones. How are 

 irregularities in their form caused ? What is said of the formation 

 of trappean rocks ? 



146. How is a sunk dike formed ? How a raised dike ? What com- 

 parison is made by Hugh Miller in speaking of the trap dikes about 

 Edinburg ? What is said of East and West Rocks in New Haven ? 

 What does Hugh Miller say about trap scenery ? How were the trap 

 rocks formed? 



147. What is said of the commotion attending their formation ? 

 What is the statement of Hugh Miller and the criticism upon it ? 

 What is said of the pillar-like form often assumed by the trap rocks ? 

 What are veins? What is said of veins in granite? 



148. State what is said of the granite boulder of which a section is 

 given. How do veins differ from dikes ? 



149. What is the vein-stone or gangue ? What is said of the man- 

 ner in which dikes and veins are formed ? What is a lode ? What 

 is drift ? In what parts of the continents does it appear ? By what 

 means was it transported to its localities ? How can it be ascertained 

 where it came from in any case ? 



150. What traces of the passage of drift are found? What is said 

 of alternate elevations and .subsidences of the earth's crust? What 

 prolonged subsidence is spoken of by Lyell ? What is said of the sub- 

 sidences and elevations of the Coal age ? 



151. By what means are pebbles, sand, and earth produced from 

 rocks ? What is soil ? What may be said of the additions to it from 

 decay ? Is the preparation of soil by disintegration of rock to be re- 

 garded only as a destructive process ? How may earth-worms and 

 ants be considered as geological workers ? 



152. Describe the work of the earth-worms. Describe that of the 

 ants. 



154. Indicate the manner in which coral reefs are built. To what 

 climates are coral animals confined? Why are there none on the 

 western coast of South America? What is the extent of the reef on 

 the coast of New Holland ? Explain the difference between fringing 

 and barrier reefs. Hc\w was Florida made ? 



155. What are atolls and lagoons? Show how an atoll is formed 

 by means of Figs. 81 and 82. 



156. What is said of the number of coral islands in the Pacific 

 Ocean ? What of the depth to which they reach in the water ? What 



