THE SURFACE OP THE EARTH. 



structure, as in fig. o, resembling fortifications seen from a 

 distance. In this case they are usually formed of calcareous, that 

 is, limestone rocks. Mountains composed of the same rocks also 



Fig 



Fig. 5. 



Fig. 0. 



Various forms of Mountains. 



frequently assume the form shown in fig. 6, as if they were cut 

 into steps forming a series of horizontal stages one above the 

 other. 



Mountains which assume the peaked or conical form, with a 

 cavity or cup-like depression at their summits, are always of 

 volcanic origin. 



Fig. 7. Barren Island in Bay of Bengal. 



In fig. 7, an example of this is presented in the case of Barren 

 island in the Bay of Bengal, consisting of a volcanic cone, 1848 

 feet high, which is frequently in a state of eruption, surrounded 

 by other peaks of similar formation. 



17. Systems or Chains of Mountains consist of series of 

 mountains, of varying elevation and form, which are often con- 

 tinued over the whole extent of a continent. 



18. Oceans. The configuration of the sea, determined by the 

 form of the lines in which it unites with the land, necessarily 

 corresponds with the configuration of the land, and such forms 

 are expressed by a system of geographical terms of correlative 

 signification. 



What a continent is to the land an ocean is to the water. This 

 term, therefore, signifies a vast tract of water, unbroken, for the 

 most part, by^any tract of land. 

 134 



