OR, PLAITS' 



prises & precipice, 12. Elevated 

 lands, almost barren, are downs, 



143. 



13. The Northern Hemisphere 

 (from the Equator to the Arctic 

 Ocean) contains three times as 

 much land as the Southern Hem- 

 isphere (from the Equator to the 

 Antarctic Ocean) ; and the sur- 

 face area of islands, in proportion 

 to that of continents, is only a 

 twenty-third part. 



The land, like the sea, is liable 

 to various disturbing phenomena. 

 The most awfully- grand of these 

 arise from eruptions, 14, and 

 earthquakes, which are connected 

 with volcanic action in the 

 depths of the earth. Volcanoes 

 are ^ believed to be produced 

 by inflammable matters, which 

 ignite by their mutual action, 

 or by the access of water and 

 air, or by the great pressure of 

 the earth. Sometimes an extent 

 of country amounting to five or 

 six hundred miles is involved in 

 these fiery discharges. There are 



teaching. 15 



certain regions where volcanoes 

 and earthquakes commonly pre- 

 vail. These are generally in or 

 near the ranges of great moun- 

 tains. Among the Andes there 

 is an uninterrupted chain of 

 volcanoes. In some districts 

 these disturbances are constant ; 

 in some parts frequent ; and in 

 others they recur at long inter- 

 vals. Volcanoes are distinguish- 

 ed from other mountains by 

 their shape, being more conical 

 than those that are non- volcanic. 

 Upon their summits there are 

 hollow cup-like depressions, 

 called craters, 15, which form 



14 



144. 



the vents of the fiery matter, 

 and cast forth volumes of smoke, 

 flame, and large pieces of a 

 metallic substance called lava, 

 16. During an eruption the 

 earth appears to be enveloped 

 in flames for miles around, while 

 the upper air is darkened with 

 dense clouds of smoke and ashes. 

 Sometimes the matter thrown 

 out of the crater is projected 

 into the air, and borne a great 



